https://projects.eclipse.org/projects/ee4j.jersey/project/jersey-media-json-jackson: Jersey JSON Jackson (2.x) entity providers support module. (Eclipse Foundation) 
package org.glassfish.jersey.jackson.internal.jackson.jaxrs.base;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.Reader;
import java.io.Writer;
import java.lang.annotation.Annotation;
import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.concurrent.atomic.AtomicReference;

import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.MultivaluedMap;
import javax.ws.rs.core.NoContentException;
import javax.ws.rs.core.Response;
import javax.ws.rs.core.StreamingOutput;
import javax.ws.rs.ext.MessageBodyReader;
import javax.ws.rs.ext.MessageBodyWriter;

import org.glassfish.jersey.jackson.internal.jackson.jaxrs.cfg.AnnotationBundleKey;
import org.glassfish.jersey.jackson.internal.jackson.jaxrs.cfg.Annotations;
import org.glassfish.jersey.jackson.internal.jackson.jaxrs.cfg.EndpointConfigBase;
import org.glassfish.jersey.jackson.internal.jackson.jaxrs.cfg.JaxRSFeature;
import org.glassfish.jersey.jackson.internal.jackson.jaxrs.cfg.MapperConfiguratorBase;
import org.glassfish.jersey.jackson.internal.jackson.jaxrs.cfg.ObjectReaderInjector;
import org.glassfish.jersey.jackson.internal.jackson.jaxrs.cfg.ObjectReaderModifier;
import org.glassfish.jersey.jackson.internal.jackson.jaxrs.cfg.ObjectWriterInjector;
import org.glassfish.jersey.jackson.internal.jackson.jaxrs.cfg.ObjectWriterModifier;
import org.glassfish.jersey.jackson.internal.jackson.jaxrs.util.ClassKey;
import org.glassfish.jersey.jackson.internal.jackson.jaxrs.util.LRUMap;

import com.fasterxml.jackson.core.JsonEncoding;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.Versioned;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.MappingIterator;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.ObjectReader;
import com.fasterxml.jackson.databind.ObjectWriter;
import com.fasterxml.jackson.databind.SerializationFeature;
import com.fasterxml.jackson.databind.type.TypeFactory;

public abstract class ProviderBase<
    THIS extends ProviderBase<THIS, MAPPER, EP_CONFIG, MAPPER_CONFIG>,
    MAPPER extends ObjectMapper,
    EP_CONFIG extends EndpointConfigBase<EP_CONFIG>,
    MAPPER_CONFIG extends MapperConfiguratorBase<MAPPER_CONFIG,MAPPER>
>
    implements
        MessageBodyReader<Object>,
        MessageBodyWriter<Object>,
        Versioned
{
    
This header is useful on Windows, trying to deal with potential XSS attacks.

/**
     * This header is useful on Windows, trying to deal with potential XSS attacks.
     */
    public final static String HEADER_CONTENT_TYPE_OPTIONS = "X-Content-Type-Options";

    
Looks like we need to worry about accidental
  data binding for types we shouldn't be handling. This is
  probably not a very good way to do it, but let's start by
  blacklisting things we are not to handle.


 (why ClassKey? since plain old Class has no hashCode() defined,
 lookups are painfully slow)

/**
     * Looks like we need to worry about accidental
     *   data binding for types we shouldn't be handling. This is
     *   probably not a very good way to do it, but let's start by
     *   blacklisting things we are not to handle.
     *<p>
     *  (why ClassKey? since plain old Class has no hashCode() defined,
     *  lookups are painfully slow)
     */
    protected final static HashSet<ClassKey> DEFAULT_UNTOUCHABLES = new HashSet<ClassKey>();
    static {
        // First, I/O things (direct matches)
        DEFAULT_UNTOUCHABLES.add(new ClassKey(InputStream.class));
        DEFAULT_UNTOUCHABLES.add(new ClassKey(Reader.class));
        DEFAULT_UNTOUCHABLES.add(new ClassKey(OutputStream.class));
        DEFAULT_UNTOUCHABLES.add(new ClassKey(Writer.class));

        // then some primitive types
        DEFAULT_UNTOUCHABLES.add(new ClassKey(char[].class));

        // 27-Apr-2012, tatu: Ugh. As per
        //   [https://github.com/FasterXML/jackson-jaxrs-json-provider/issues/12]
        //  better revert this back, to make them untouchable again.
        DEFAULT_UNTOUCHABLES.add(new ClassKey(String.class));
        DEFAULT_UNTOUCHABLES.add(new ClassKey(byte[].class));
    }

    
These are classes that we never use for reading
(never try to deserialize instances of these types).

/**
     * These are classes that we never use for reading
     * (never try to deserialize instances of these types).
     */
    public final static Class<?>[] DEFAULT_UNREADABLES = new Class<?>[] {
        InputStream.class, Reader.class
    };

    
These are classes that we never use for writing
(never try to serialize instances of these types).

/**
     * These are classes that we never use for writing
     * (never try to serialize instances of these types).
     */
    public final static Class<?>[] DEFAULT_UNWRITABLES = new Class<?>[] {
        InputStream.class, // as per [Issue#19]
        OutputStream.class, Writer.class,
        StreamingOutput.class, Response.class
    };

    protected final static int JAXRS_FEATURE_DEFAULTS = JaxRSFeature.collectDefaults();
    
    /*
    /**********************************************************
    /* General configuration
    /**********************************************************
     */

    
Helper object used for encapsulating configuration aspects of ObjectMapper 
/**
     * Helper object used for encapsulating configuration aspects
     * of {@link ObjectMapper}
     */
    protected final MAPPER_CONFIG _mapperConfig;
    
    
Map that contains overrides to default list of untouchable
types: true meaning that entry is untouchable,
false that is is not.

/**
     * Map that contains overrides to default list of untouchable
     * types: <code>true</code> meaning that entry is untouchable,
     * <code>false</code> that is is not.
     */
    protected HashMap<ClassKey,Boolean> _cfgCustomUntouchables;

    
Whether we want to actually check that Jackson has
a serializer for given type. Since this should generally
be the case (due to auto-discovery) and since the call
to check availability can be bit expensive, defaults to false.

/**
     * Whether we want to actually check that Jackson has
     * a serializer for given type. Since this should generally
     * be the case (due to auto-discovery) and since the call
     * to check availability can be bit expensive, defaults to false.
     */
    protected boolean _cfgCheckCanSerialize = false;

    
Whether we want to actually check that Jackson has
a deserializer for given type. Since this should generally
be the case (due to auto-discovery) and since the call
to check availability can be bit expensive, defaults to false.

/**
     * Whether we want to actually check that Jackson has
     * a deserializer for given type. Since this should generally
     * be the case (due to auto-discovery) and since the call
     * to check availability can be bit expensive, defaults to false.
     */
    protected boolean _cfgCheckCanDeserialize = false;

    
Feature flags set.

Since:2.3
/**
     * Feature flags set.
     * 
     * @since 2.3
     */
    protected int _jaxRSFeatures;

    
View to use for reading if none defined for the end point.

/**
     * View to use for reading if none defined for the end point.
     */
    protected Class<?> _defaultReadView;

    
View to use for writing if none defined for the end point.

/**
     * View to use for writing if none defined for the end point.
     */
    protected Class<?> _defaultWriteView;
    
    /*
    /**********************************************************
    /* Excluded types
    /**********************************************************
     */

    public final static HashSet<ClassKey> _untouchables = DEFAULT_UNTOUCHABLES;

    public final static Class<?>[] _unreadableClasses = DEFAULT_UNREADABLES;

    public final static Class<?>[] _unwritableClasses = DEFAULT_UNWRITABLES;

    /*
    /**********************************************************
    /* Bit of caching
    /**********************************************************
     */

    
Cache for resolved endpoint configurations when reading JSON data

/**
     * Cache for resolved endpoint configurations when reading JSON data
     */
    protected final LRUMap<AnnotationBundleKey, EP_CONFIG> _readers
        = new LRUMap<AnnotationBundleKey, EP_CONFIG>(16, 120);

    
Cache for resolved endpoint configurations when writing JSON data

/**
     * Cache for resolved endpoint configurations when writing JSON data
     */
    protected final LRUMap<AnnotationBundleKey, EP_CONFIG> _writers
        = new LRUMap<AnnotationBundleKey, EP_CONFIG>(16, 120);

    protected final AtomicReference<IOException> _noContentExceptionRef
        = new AtomicReference<IOException>();

    /*
    /**********************************************************
    /* Life-cycle
    /**********************************************************
     */

    protected ProviderBase(MAPPER_CONFIG mconfig) {
        _mapperConfig = mconfig;
        _jaxRSFeatures = JAXRS_FEATURE_DEFAULTS;
    }

    
Constructor that is only added to resolve
issue #10; problems with combination of
RESTeasy and CDI.
Should NOT be used by any code explicitly; only exists
for proxy support.

/**
     * Constructor that is only added to resolve
     * issue #10; problems with combination of
     * RESTeasy and CDI.
     * Should NOT be used by any code explicitly; only exists
     * for proxy support.
     */
    @Deprecated // just to denote it should NOT be directly called; will NOT be removed
    protected ProviderBase() {
        _mapperConfig = null;
        _jaxRSFeatures = JAXRS_FEATURE_DEFAULTS;
    }
    
    /*
    /**********************************************************
    /* Configuring
    /**********************************************************
     */

    
Method for defining whether actual detection for existence of a deserializer for type should be done when isReadable is called. 
/**
     * Method for defining whether actual detection for existence of
     * a deserializer for type should be done when {@link #isReadable}
     * is called.
     */
    public void checkCanDeserialize(boolean state) { _cfgCheckCanDeserialize = state; }

    
Method for defining whether actual detection for existence of a serializer for type should be done when isWriteable is called. 
/**
     * Method for defining whether actual detection for existence of
     * a serializer for type should be done when {@link #isWriteable}
     * is called.
     */
    public void checkCanSerialize(boolean state) { _cfgCheckCanSerialize = state; }

    
Method for marking specified type as "untouchable", meaning that provider
will not try to read or write values of this type (or its subtypes).

Params:
  • type – Type to consider untouchable; can be any kind of class,
  including abstract class or interface. No instance of this type
  (including subtypes, i.e. types assignable to this type) will
  be read or written by provider
/**
     * Method for marking specified type as "untouchable", meaning that provider
     * will not try to read or write values of this type (or its subtypes).
     * 
     * @param type Type to consider untouchable; can be any kind of class,
     *   including abstract class or interface. No instance of this type
     *   (including subtypes, i.e. types assignable to this type) will
     *   be read or written by provider
     */
    public void addUntouchable(Class<?> type)
    {
        if (_cfgCustomUntouchables == null) {
            _cfgCustomUntouchables = new HashMap<ClassKey,Boolean>();
        }
        _cfgCustomUntouchables.put(new ClassKey(type), Boolean.TRUE);
    }

    
Method for removing definition of specified type as untouchable:
usually only 

Since:2.2
/**
     * Method for removing definition of specified type as untouchable:
     * usually only 
     * 
     * @since 2.2
     */
    public void removeUntouchable(Class<?> type)
    {
        if (_cfgCustomUntouchables == null) {
            _cfgCustomUntouchables = new HashMap<ClassKey,Boolean>();
        }
        _cfgCustomUntouchables.put(new ClassKey(type), Boolean.FALSE);
    }
    
    
Method for configuring which annotation sets to use (including none).
Annotation sets are defined in order decreasing precedence; that is,
first one has the priority over following ones.

Params:
  • annotationsToUse – Ordered list of annotation sets to use; if null,
   default
/**
     * Method for configuring which annotation sets to use (including none).
     * Annotation sets are defined in order decreasing precedence; that is,
     * first one has the priority over following ones.
     * 
     * @param annotationsToUse Ordered list of annotation sets to use; if null,
     *    default
     */
    public void setAnnotationsToUse(Annotations[] annotationsToUse) {
        _mapperConfig.setAnnotationsToUse(annotationsToUse);
    }
    
    
Method that can be used to directly define ObjectMapper to use for serialization and deserialization; if null, will use the standard provider discovery from context instead. Default setting is null. 
/**
     * Method that can be used to directly define {@link ObjectMapper} to use
     * for serialization and deserialization; if null, will use the standard
     * provider discovery from context instead. Default setting is null.
     */
    public void setMapper(MAPPER m) {
        _mapperConfig.setMapper(m);
    }

    
Method for specifying JSON View to use for reading content
when end point does not have explicit View annotations.

Since:2.3
/**
     * Method for specifying JSON View to use for reading content
     * when end point does not have explicit View annotations.
     * 
     * @since 2.3
     */
    public THIS setDefaultReadView(Class<?> view) {
        _defaultReadView = view;
        return _this();
    }

    
Method for specifying JSON View to use for reading content
when end point does not have explicit View annotations.

Since:2.3
/**
     * Method for specifying JSON View to use for reading content
     * when end point does not have explicit View annotations.
     * 
     * @since 2.3
     */
    public THIS setDefaultWriteView(Class<?> view) {
        _defaultWriteView = view;
        return _this();
    }

    
Method for specifying JSON View to use for reading and writing content
when end point does not have explicit View annotations.
Functionally equivalent to:

 setDefaultReadView(view);
 setDefaultWriteView(view);


Since:2.3
/**
     * Method for specifying JSON View to use for reading and writing content
     * when end point does not have explicit View annotations.
     * Functionally equivalent to:
     *<code>
     *  setDefaultReadView(view);
     *  setDefaultWriteView(view);
     *</code>
     * 
     * @since 2.3
     */
    public THIS setDefaultView(Class<?> view) {
        _defaultReadView = _defaultWriteView = view;
        return _this();
    }
    
    // // // JaxRSFeature config
    
    public THIS configure(JaxRSFeature feature, boolean state) {
        return state ? enable(feature) : disable(feature);
    }

    public THIS enable(JaxRSFeature feature) {
        _jaxRSFeatures |= feature.getMask();
        return _this();
    }

    public THIS enable(JaxRSFeature first, JaxRSFeature... f2) {
        _jaxRSFeatures |= first.getMask();
        for (JaxRSFeature f : f2) {
            _jaxRSFeatures |= f.getMask();
        }
        return _this();
    }

    public THIS disable(JaxRSFeature feature) {
        _jaxRSFeatures &= ~feature.getMask();
        return _this();
    }

    public THIS disable(JaxRSFeature first, JaxRSFeature... f2) {
        _jaxRSFeatures &= ~first.getMask();
        for (JaxRSFeature f : f2) {
            _jaxRSFeatures &= ~f.getMask();
        }
        return _this();
    }

    public boolean isEnabled(JaxRSFeature f) {
        return (_jaxRSFeatures & f.getMask()) != 0;
    }
    
    // // // DeserializationFeature

    public THIS configure(DeserializationFeature f, boolean state) {
        _mapperConfig.configure(f, state);
        return _this();
    }
    
    public THIS enable(DeserializationFeature f) {
        _mapperConfig.configure(f, true);
        return _this();
    }

    public THIS disable(DeserializationFeature f) {
        _mapperConfig.configure(f, false);
        return _this();
    }
    
    // // // SerializationFeature

    public THIS configure(SerializationFeature f, boolean state) {
        _mapperConfig.configure(f, state);
        return _this();
    }

    public THIS enable(SerializationFeature f) {
        _mapperConfig.configure(f, true);
        return _this();
    }

    public THIS disable(SerializationFeature f) {
        _mapperConfig.configure(f, false);
        return _this();
    }
    
    // // // JsonParser/JsonGenerator
    
    public THIS enable(JsonParser.Feature f) {
        _mapperConfig.configure(f, true);
        return _this();
    }

    public THIS enable(JsonGenerator.Feature f) {
        _mapperConfig.configure(f, true);
        return _this();
    }

    public THIS disable(JsonParser.Feature f) {
        _mapperConfig.configure(f, false);
        return _this();
    }

    public THIS disable(JsonGenerator.Feature f) {
        _mapperConfig.configure(f, false);
        return _this();
    }

    public THIS configure(JsonParser.Feature f, boolean state) {
        _mapperConfig.configure(f, state);
        return _this();
    }

    public THIS configure(JsonGenerator.Feature f, boolean state) {
        _mapperConfig.configure(f, state);
        return _this();
    }

    /*
    /**********************************************************
    /* Abstract methods sub-classes need to implement
    /**********************************************************
     */

    
Helper method used to check whether given media type
is supported by this provider for read operations
(when binding input data such as POST body).

 Default implementation simply calls hasMatchingMediaType. 
Since:2.3
/**
     * Helper method used to check whether given media type
     * is supported by this provider for read operations
     * (when binding input data such as POST body).
     *<p>
     * Default implementation simply calls {@link #hasMatchingMediaType}.
     * 
     * @since 2.3
     */
    protected boolean hasMatchingMediaTypeForReading(MediaType mediaType) {
        return hasMatchingMediaType(mediaType);
    }

    
Helper method used to check whether given media type
is supported by this provider for writing operations,
such as when converting response object to response
body of request (like GET or POST).

 Default implementation simply calls hasMatchingMediaType. 
Since:2.3
/**
     * Helper method used to check whether given media type
     * is supported by this provider for writing operations,
     * such as when converting response object to response
     * body of request (like GET or POST).
     *<p>
     * Default implementation simply calls {@link #hasMatchingMediaType}.
     * 
     * @since 2.3
     */
    protected boolean hasMatchingMediaTypeForWriting(MediaType mediaType) {
        return hasMatchingMediaType(mediaType);
    }
    
    
Helper method used to check whether given media type
is supported by this provider.

Since:2.2
/**
     * Helper method used to check whether given media type
     * is supported by this provider.
     * 
     * @since 2.2
     */
    protected abstract boolean hasMatchingMediaType(MediaType mediaType);

    
Helper method that is called if no mapper has been explicitly configured.

/**
     * Helper method that is called if no mapper has been explicitly configured.
     */
    protected abstract MAPPER _locateMapperViaProvider(Class<?> type, MediaType mediaType);
    
    protected EP_CONFIG _configForReading(MAPPER mapper,
        Annotation[] annotations, Class<?> defaultView)
    {
//        ObjectReader r = _readerInjector.getAndClear();
        ObjectReader r;
        if (defaultView != null) {
            r = mapper.readerWithView(defaultView);
        } else {
            r = mapper.reader();
        }
        return _configForReading(r, annotations);
    }

    protected EP_CONFIG _configForWriting(MAPPER mapper,
        Annotation[] annotations, Class<?> defaultView)
    {
//        ObjectWriter w = _writerInjector.getAndClear();
        ObjectWriter w;
        if (defaultView != null) {
            w = mapper.writerWithView(defaultView);
        } else {
            w = mapper.writer();
        }
        return _configForWriting(w, annotations);
    }

    protected abstract EP_CONFIG _configForReading(ObjectReader reader,
            Annotation[] annotations);

    protected abstract EP_CONFIG _configForWriting(ObjectWriter writer,
        Annotation[] annotations);

    /*
    /**********************************************************
    /* Partial MessageBodyWriter impl
    /**********************************************************
     */

    
Method that JAX-RS container calls to try to figure out
serialized length of given value. Since computation of
this length is about as expensive as serialization itself,
implementation will return -1 to denote "not known", so
that container will determine length from actual serialized
output (if needed).

/**
     * Method that JAX-RS container calls to try to figure out
     * serialized length of given value. Since computation of
     * this length is about as expensive as serialization itself,
     * implementation will return -1 to denote "not known", so
     * that container will determine length from actual serialized
     * output (if needed).
     */
    @Override
    public long getSize(Object value, Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType)
    {
        /* In general figuring output size requires actual writing; usually not
         * worth it to write everything twice.
         */
        return -1;
    }
    
    
Method that JAX-RS container calls to try to check whether given value (of specified type) can be serialized by this provider. Implementation will first check that expected media type is expected one (by call to hasMatchingMediaType); then verify that type is not one of "untouchable" types (types we will never automatically handle), and finally that there is a serializer for type (iff checkCanSerialize has been called with true argument -- otherwise assumption is there will be a handler) 
/**
     * Method that JAX-RS container calls to try to check whether
     * given value (of specified type) can be serialized by
     * this provider.
     * Implementation will first check that expected media type is
     * expected one (by call to {@link #hasMatchingMediaType}); then verify
     * that type is not one of "untouchable" types (types we will never
     * automatically handle), and finally that there is a serializer
     * for type (iff {@link #checkCanSerialize} has been called with
     * true argument -- otherwise assumption is there will be a handler)
     */
    @Override
    public boolean isWriteable(Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType)
    {
        if (!hasMatchingMediaType(mediaType)) {
            return false;
        }
        Boolean customUntouchable = _findCustomUntouchable(type);
        if (customUntouchable != null) {
            // negation: Boolean.TRUE means untouchable -> can not write
            return !customUntouchable.booleanValue();
        }
        /* Ok: looks like we must weed out some core types here; ones that
         * make no sense to try to bind from JSON:
         */
        if (_isIgnorableForWriting(new ClassKey(type))) {
            return false;
        }
        // but some are interface/abstract classes, so
        for (Class<?> cls : _unwritableClasses) {
            if (cls.isAssignableFrom(type)) {
                return false;
            }
        }
        // Also: if we really want to verify that we can deserialize, we'll check:
        if (_cfgCheckCanSerialize) {
            if (!locateMapper(type, mediaType).canSerialize(type)) {
                return false;
            }
        }
        return true;
    }

    
Method that JAX-RS container calls to serialize given value.

/**
     * Method that JAX-RS container calls to serialize given value.
     */
    @Override
    public void writeTo(Object value, Class<?> type, Type genericType, Annotation[] annotations,
            MediaType mediaType,
            MultivaluedMap<String,Object> httpHeaders, OutputStream entityStream) 
        throws IOException
    {
        EP_CONFIG endpoint = _endpointForWriting(value, type, genericType, annotations,
                mediaType, httpHeaders);

        // Any headers we should write?
        _modifyHeaders(value, type, genericType, annotations, httpHeaders, endpoint);
        
        ObjectWriter writer = endpoint.getWriter();

        // Where can we find desired encoding? Within HTTP headers?
        JsonEncoding enc = findEncoding(mediaType, httpHeaders);
        JsonGenerator g = _createGenerator(writer, entityStream, enc);
        boolean ok = false;

        try {
            // Want indentation?
            if (writer.isEnabled(SerializationFeature.INDENT_OUTPUT)) {
                g.useDefaultPrettyPrinter();
            }
            JavaType rootType = null;

            if ((genericType != null) && (value != null)) {
                // 10-Jan-2011, tatu: as per [JACKSON-456], it's not safe to just force root
                //    type since it prevents polymorphic type serialization. Since we really
                //    just need this for generics, let's only use generic type if it's truly generic.

                if (!(genericType instanceof Class<?>)) { // generic types are other impls of 'java.lang.reflect.Type'
                    // This is still not exactly right; should root type be further
                    // specialized with 'value.getClass()'? Let's see how well this works before
                    // trying to come up with more complete solution.

                    // 18-Mar-2015, tatu: As per [#60], there is now a problem with non-polymorphic lists,
                    //    since forcing of type will then force use of content serializer, which is
                    //    generally not the intent. Fix may require addition of functionality in databind

                    TypeFactory typeFactory = writer.getTypeFactory();
                    JavaType baseType = typeFactory.constructType(genericType);
                    rootType = typeFactory.constructSpecializedType(baseType, type);
                    /* 26-Feb-2011, tatu: To help with [JACKSON-518], we better recognize cases where
                     *    type degenerates back into "Object.class" (as is the case with plain TypeVariable,
                     *    for example), and not use that.
                     */
                    if (rootType.getRawClass() == Object.class) {
                        rootType = null;
                    }
                }
            }

            // Most of the configuration now handled through EndpointConfig, ObjectWriter
            // but we may need to force root type:
            if (rootType != null) {
                writer = writer.forType(rootType);
            }
            value = endpoint.modifyBeforeWrite(value);

            // [Issue#32]: allow modification by filter-injectible thing
            ObjectWriterModifier mod = ObjectWriterInjector.getAndClear();
            if (mod != null) {
                writer = mod.modify(endpoint, httpHeaders, value, writer, g);
            }

            writer.writeValue(g, value);
            ok = true;
        } finally {
            if (ok) {
                g.close();
            } else {
                try {
                    g.close();
                } catch (Exception e) { }
            }
        }
    }

    
Helper method to use for determining desired output encoding.
For now, will always just use UTF-8...

/**
     * Helper method to use for determining desired output encoding.
     * For now, will always just use UTF-8...
     */
    protected JsonEncoding findEncoding(MediaType mediaType, MultivaluedMap<String,Object> httpHeaders)
    {
        return JsonEncoding.UTF8;
    }

    
Overridable method used for adding optional response headers before
serializing response object.

/**
     * Overridable method used for adding optional response headers before
     * serializing response object.
     */
    protected void _modifyHeaders(Object value, Class<?> type, Type genericType, Annotation[] annotations,
            MultivaluedMap<String,Object> httpHeaders,
            EP_CONFIG endpoint)
        throws IOException
    {
        // Add "nosniff" header?
        if (isEnabled(JaxRSFeature.ADD_NO_SNIFF_HEADER)) {
            httpHeaders.add(HEADER_CONTENT_TYPE_OPTIONS, "nosniff");
        }
    }

    
Overridable helper method called to create a JsonGenerator for writing contents into given raw OutputStream. 
Since:2.3
/**
     * Overridable helper method called to create a {@link JsonGenerator} for writing
     * contents into given raw {@link OutputStream}.
     * 
     * @since 2.3
     */
    protected JsonGenerator _createGenerator(ObjectWriter writer, OutputStream rawStream, JsonEncoding enc)
        throws IOException
    {
        JsonGenerator g = writer.getFactory().createGenerator(rawStream, enc);
        // Important: we are NOT to close the underlying stream after
        // mapping, so we need to instruct generator
        g.disable(JsonGenerator.Feature.AUTO_CLOSE_TARGET);
        return g;
    }

    protected EP_CONFIG _endpointForWriting(Object value, Class<?> type, Type genericType,
            Annotation[] annotations, MediaType mediaType, MultivaluedMap<String,Object> httpHeaders)
    {
        // 29-Jun-2016, tatu: As per [jaxrs-providers#86] allow skipping caching
        if (!isEnabled(JaxRSFeature.CACHE_ENDPOINT_WRITERS)) {
            return _configForWriting(locateMapper(type, mediaType), annotations, _defaultWriteView);
        }

        EP_CONFIG endpoint;
        AnnotationBundleKey key = new AnnotationBundleKey(annotations, type);
        synchronized (_writers) {
            endpoint = _writers.get(key);
        }
        // not yet resolved (or not cached any more)? Resolve!
        if (endpoint == null) {
            MAPPER mapper = locateMapper(type, mediaType);
            endpoint = _configForWriting(mapper, annotations, _defaultWriteView);
            // and cache for future reuse
            synchronized (_writers) {
                _writers.put(key.immutableKey(), endpoint);
            }
        }
        return endpoint;
    }

    /*
    /**********************************************************
    /* MessageBodyReader impl
    /**********************************************************
     */
    
    
Method that JAX-RS container calls to try to check whether values of given type (and media type) can be deserialized by this provider. Implementation will first check that expected media type is a JSON type (via call to hasMatchingMediaType); then verify that type is not one of "untouchable" types (types we will never automatically handle), and finally that there is a deserializer for type (iff checkCanDeserialize has been called with true argument -- otherwise assumption is there will be a handler) 
/**
     * Method that JAX-RS container calls to try to check whether
     * values of given type (and media type) can be deserialized by
     * this provider.
     * Implementation will first check that expected media type is
     * a JSON type (via call to {@link #hasMatchingMediaType});
     * then verify
     * that type is not one of "untouchable" types (types we will never
     * automatically handle), and finally that there is a deserializer
     * for type (iff {@link #checkCanDeserialize} has been called with
     * true argument -- otherwise assumption is there will be a handler)
     */
    @Override
    public boolean isReadable(Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType)
    {
        if (!hasMatchingMediaType(mediaType)) {
            return false;
        }
        Boolean customUntouchable = _findCustomUntouchable(type);
        if (customUntouchable != null) {
            // negation: Boolean.TRUE means untouchable -> can not write
            return !customUntouchable.booleanValue();
        }
        /* Ok: looks like we must weed out some core types here; ones that
         * make no sense to try to bind from JSON:
         */
        if (_isIgnorableForReading(new ClassKey(type))) {
            return false;
        }
        // and there are some other abstract/interface types to exclude too:
        for (Class<?> cls : _unreadableClasses) {
            if (cls.isAssignableFrom(type)) {
                return false;
            }
        }
        // Finally: if we really want to verify that we can serialize, we'll check:
        if (_cfgCheckCanDeserialize) {
            if (_isSpecialReadable(type)) {
                return true;
            }
            ObjectMapper mapper = locateMapper(type, mediaType);
            if (!mapper.canDeserialize(mapper.constructType(type))) {
                return false;
            }
        }
        return true;
    }

    
Method that JAX-RS container calls to deserialize given value.

/**
     * Method that JAX-RS container calls to deserialize given value.
     */
    @Override
    public Object readFrom(Class<Object> type, Type genericType, Annotation[] annotations,
            MediaType mediaType, MultivaluedMap<String,String> httpHeaders,
            InputStream entityStream) 
        throws IOException
    {
        EP_CONFIG endpoint = _endpointForReading(type, genericType, annotations,
                mediaType, httpHeaders);
        
        ObjectReader reader = endpoint.getReader();
        JsonParser p = _createParser(reader, entityStream);
        
        // If null is returned, considered to be empty stream
        // 05-Apr-2014, tatu: As per [Issue#49], behavior here is configurable.
        if (p == null || p.nextToken() == null) {
            if (JaxRSFeature.ALLOW_EMPTY_INPUT.enabledIn(_jaxRSFeatures)) {
                return null;
            }
            /* 05-Apr-2014, tatu: Trick-ee. NoContentFoundException only available in JAX-RS 2.0...
             *   so need bit of obfuscated code to reach it.
             */
            IOException fail = _noContentExceptionRef.get();
            if (fail == null) {
                fail = _createNoContentException();
            }
            throw fail;
        }
        Class<?> rawType = type;
        if (rawType == JsonParser.class) {
            return p;
        }
        final TypeFactory tf = reader.getTypeFactory();
        final JavaType resolvedType = tf.constructType(genericType);

        // 09-Jul-2015, tatu: As per [jaxrs-providers#69], handle MappingIterator too
        boolean multiValued = (rawType == MappingIterator.class);
        
        if (multiValued) {
            JavaType[] contents = tf.findTypeParameters(resolvedType, MappingIterator.class);
            JavaType valueType = (contents == null || contents.length == 0)
                    ? tf.constructType(Object.class) : contents[0];
            reader = reader.forType(valueType);
        } else {
            reader = reader.forType(resolvedType);
        }

        // [Issue#32]: allow modification by filter-injectable thing
        ObjectReaderModifier mod = ObjectReaderInjector.getAndClear();
        if (mod != null) {
            reader = mod.modify(endpoint, httpHeaders, resolvedType, reader, p);
        }
        
        if (multiValued) {
            return reader.readValues(p);
        }
        return reader.readValue(p);
    }

    
Overridable helper method called to create a JsonParser for reading contents of given raw InputStream. May return null to indicate that Stream is empty; that is, contains no content. 
Since:2.2
/**
     * Overridable helper method called to create a {@link JsonParser} for reading
     * contents of given raw {@link InputStream}.
     * May return null to indicate that Stream is empty; that is, contains no
     * content.
     * 
     * @since 2.2
     */
    protected JsonParser _createParser(ObjectReader reader, InputStream rawStream)
        throws IOException
    {
        JsonParser p = reader.getFactory().createParser(rawStream);
        // Important: we are NOT to close the underlying stream after
        // mapping, so we need to instruct parser:
        p.disable(JsonParser.Feature.AUTO_CLOSE_SOURCE);
        return p;
    }

    
Overridable helper method that will basically fetch representation of the endpoint that can be used to get ObjectReader to use for deserializing content 
Since:2.8
/**
     * Overridable helper method that will basically fetch representation of the
     * endpoint that can be used to get {@link ObjectReader} to use for deserializing
     * content
     *
     * @since 2.8
     */
    protected EP_CONFIG _endpointForReading(Class<Object> type, Type genericType, Annotation[] annotations,
            MediaType mediaType, MultivaluedMap<String,String> httpHeaders)
    {
        // 29-Jun-2016, tatu: As per [jaxrs-providers#86] allow skipping caching
        if (!isEnabled(JaxRSFeature.CACHE_ENDPOINT_READERS)) {
            return _configForReading(locateMapper(type, mediaType), annotations, _defaultReadView);
        }

        EP_CONFIG endpoint;
        AnnotationBundleKey key = new AnnotationBundleKey(annotations, type);
        synchronized (_readers) {
            endpoint = _readers.get(key);
        }
        // not yet resolved (or not cached any more)? Resolve!
        if (endpoint == null) {
            MAPPER mapper = locateMapper(type, mediaType);
            endpoint = _configForReading(mapper, annotations, _defaultReadView);
            // and cache for future reuse
            synchronized (_readers) {
                _readers.put(key.immutableKey(), endpoint);
            }
        }
        return endpoint;
    }

    /*
    /**********************************************************
    /* Overridable helper methods
    /**********************************************************
     */

    
Method called to locate ObjectMapper to use for serialization and deserialization. Exact logic depends on setting of JaxRSFeature.DYNAMIC_OBJECT_MAPPER_LOOKUP. 
 If JaxRSFeature.DYNAMIC_OBJECT_MAPPER_LOOKUP is disabled (default setting unless changed), behavior is as follows: 
    

  1. If an instance has been explicitly defined by setMapper (or non-null instance passed in constructor), that will be used. 
    2. 

  2. If not, will try to locate it using standard JAX-RS
ContextResolver mechanism, if it has been properly configured
to access it (by JAX-RS runtime).
 
    3. 

  3. Finally, if no mapper is found, will return a default unconfigured ObjectMapper instance (one constructed with default constructor and not modified in any way) 
    4. 



 If JaxRSFeature.DYNAMIC_OBJECT_MAPPER_LOOKUP is enabled, steps 1 and 2 are reversed, such that JAX-RS ContextResolver
is first used, and only if none is defined will configured mapper be used.

Params:
  • type – Class of object being serialized or deserialized;
  not checked at this point, since it is assumed that unprocessable
  classes have been already weeded out,
  but will be passed to ContextResolver as is.
  • mediaType – Declared media type for the instance to process:
  not used by this method,
  but will be passed to ContextResolver as is.
/**
     * Method called to locate {@link ObjectMapper} to use for serialization
     * and deserialization. Exact logic depends on setting of
     * {@link JaxRSFeature#DYNAMIC_OBJECT_MAPPER_LOOKUP}.
     * 
     *<p>
     * If {@link JaxRSFeature#DYNAMIC_OBJECT_MAPPER_LOOKUP} is disabled (default
     * setting unless changed), behavior is as follows:
     *<ol>
     * <li>If an instance has been explicitly defined by
     * {@link #setMapper} (or non-null instance passed in constructor), that
     * will be used.
     *  </li>
     * <li>If not, will try to locate it using standard JAX-RS
     * <code>ContextResolver</code> mechanism, if it has been properly configured
     * to access it (by JAX-RS runtime).
     *  </li>
     * <li>Finally, if no mapper is found, will return a default unconfigured
     * {@link ObjectMapper} instance (one constructed with default constructor
     * and not modified in any way)
     *   </li>
     *</ol>
     *<p>
     * If {@link JaxRSFeature#DYNAMIC_OBJECT_MAPPER_LOOKUP} is enabled, steps
     * 1 and 2 are reversed, such that JAX-RS <code>ContextResolver</code>
     * is first used, and only if none is defined will configured mapper be used.
     *
     * @param type Class of object being serialized or deserialized;
     *   not checked at this point, since it is assumed that unprocessable
     *   classes have been already weeded out,
     *   but will be passed to <code>ContextResolver</code> as is.
     * @param mediaType Declared media type for the instance to process:
     *   not used by this method,
     *   but will be passed to <code>ContextResolver</code> as is.
     */
    public MAPPER locateMapper(Class<?> type, MediaType mediaType)
    {
        // 29-Jun-2016, tatu: As per [jaxrs-providers#86] may want to do provider lookup first
        if (isEnabled(JaxRSFeature.DYNAMIC_OBJECT_MAPPER_LOOKUP)) {
            MAPPER m = _locateMapperViaProvider(type, mediaType);
            if (m == null) {
                m = _mapperConfig.getConfiguredMapper();
                if (m == null) {
                    m = _mapperConfig.getDefaultMapper();
                }
            }
            return m;
        }

        // Otherwise start with (pre-)configured Mapper and only check provider
        // if not found
        
        MAPPER m = _mapperConfig.getConfiguredMapper();
        if (m == null) {
            // If not, maybe we can get one configured via context?
            m = _locateMapperViaProvider(type, mediaType);
            if (m == null) {
                // If not, let's get the fallback default instance
                m = _mapperConfig.getDefaultMapper();
            }
        }
        return m;
    }

    
Overridable helper method used to allow handling of somewhat special
types for reading

Since:2.2
/**
     * Overridable helper method used to allow handling of somewhat special
     * types for reading
     * 
     * @since 2.2
     */
    protected boolean _isSpecialReadable(Class<?> type) {
        return JsonParser.class == type;
    }

    
Overridable helper method called to check whether given type is a known
"ignorable type" (in context of reading), values of which are not bound
from content.

Since:2.6
/**
     * Overridable helper method called to check whether given type is a known
     * "ignorable type" (in context of reading), values of which are not bound
     * from content.
     *
     * @since 2.6
     */
    protected boolean _isIgnorableForReading(ClassKey typeKey)
    {
        return _untouchables.contains(typeKey);
    }

    
Overridable helper method called to check whether given type is a known
"ignorable type" (in context of reading), values of which
can not be written out.

Since:2.6
/**
     * Overridable helper method called to check whether given type is a known
     * "ignorable type" (in context of reading), values of which
     * can not be written out.
     *
     * @since 2.6
     */
    protected boolean _isIgnorableForWriting(ClassKey typeKey)
    {
        return _untouchables.contains(typeKey);
    }
    
    
Since:2.4
/**
     * @since 2.4
     */
    protected IOException _createNoContentException()
    {
     return new NoContentException("No content (empty input stream)");
    }

    /*
    /**********************************************************
    /* Private/sub-class helper methods
    /**********************************************************
     */

    protected static boolean _containedIn(Class<?> mainType, HashSet<ClassKey> set)
    {
        if (set != null) {
            ClassKey key = new ClassKey(mainType);
            // First: type itself?
            if (set.contains(key)) return true;
            // Then supertypes (note: will not contain Object.class)
            for (Class<?> cls : findSuperTypes(mainType, null)) {
                key.reset(cls);
                if (set.contains(key)) return true;
            }
        }
        return false;
    }

    protected Boolean _findCustomUntouchable(Class<?> mainType)
    {
        if (_cfgCustomUntouchables != null) {
            ClassKey key = new ClassKey(mainType);
            // First: type itself?
            Boolean b = _cfgCustomUntouchables.get(key);
            if (b != null) {
                return b;
            }
            // Then supertypes (note: will not contain Object.class)
            for (Class<?> cls : findSuperTypes(mainType, null)) {
                key.reset(cls);
                b = _cfgCustomUntouchables.get(key);
                if (b != null) {
                    return b;
                }
            }
        }
        return null;
    }
    
    protected static List<Class<?>> findSuperTypes(Class<?> cls, Class<?> endBefore)
    {
        return findSuperTypes(cls, endBefore, new ArrayList<Class<?>>(8));
    }

    protected static List<Class<?>> findSuperTypes(Class<?> cls, Class<?> endBefore, List<Class<?>> result)
    {
        _addSuperTypes(cls, endBefore, result, false);
        return result;
    }
    
    protected static void _addSuperTypes(Class<?> cls, Class<?> endBefore, Collection<Class<?>> result, boolean addClassItself)
    {
        if (cls == endBefore || cls == null || cls == Object.class) {
            return;
        }
        if (addClassItself) {
            if (result.contains(cls)) { // already added, no need to check supers
                return;
            }
            result.add(cls);
        }
        for (Class<?> intCls : cls.getInterfaces()) {
            _addSuperTypes(intCls, endBefore, result, true);
        }
        _addSuperTypes(cls.getSuperclass(), endBefore, result, true);
    }

    @SuppressWarnings("unchecked")
    private final THIS _this() {
        return (THIS) this;
    }
}