Jackson is "the Java JSON library" or "the best JSON parser for Java". Or simply as "JSON for Java".

Jackson Annotations Source Code files are provided in the source packge (jackson-annotations-2.12.4-sources.jar). You can download it at Jackson Maven Website.

You can also browse Jackson Annotations Source Code below:

⏎ com/fasterxml/jackson/databind/ser/impl/UnwrappingBeanSerializer.java

package com.fasterxml.jackson.databind.ser.impl;

import com.fasterxml.jackson.core.JsonGenerator;

import com.fasterxml.jackson.databind.*;
import com.fasterxml.jackson.databind.jsontype.TypeSerializer;
import com.fasterxml.jackson.databind.ser.BeanPropertyWriter;
import com.fasterxml.jackson.databind.ser.std.BeanSerializerBase;
import com.fasterxml.jackson.databind.util.NameTransformer;

import java.io.IOException;
import java.util.Set;

public class UnwrappingBeanSerializer
    extends BeanSerializerBase
    implements java.io.Serializable
{
    private static final long serialVersionUID = 1L;

    /**
     * Transformer used to add prefix and/or suffix for properties
     * of unwrapped POJO.
     */
    protected final NameTransformer _nameTransformer;
    
    /*
    /**********************************************************
    /* Life-cycle: constructors
    /**********************************************************
     */

    /**
     * Constructor used for creating unwrapping instance of a
     * standard <code>BeanSerializer</code>
     */
    public UnwrappingBeanSerializer(BeanSerializerBase src, NameTransformer transformer) {
        super(src, transformer);
        _nameTransformer = transformer;
    }

    public UnwrappingBeanSerializer(UnwrappingBeanSerializer src,
            ObjectIdWriter objectIdWriter) {
        super(src, objectIdWriter);
        _nameTransformer = src._nameTransformer;
    }

    public UnwrappingBeanSerializer(UnwrappingBeanSerializer src,
            ObjectIdWriter objectIdWriter, Object filterId) {
        super(src, objectIdWriter, filterId);
        _nameTransformer = src._nameTransformer;
    }

    protected UnwrappingBeanSerializer(UnwrappingBeanSerializer src, Set<String> toIgnore) {
        this(src, toIgnore, null);
    }

    protected UnwrappingBeanSerializer(UnwrappingBeanSerializer src, Set<String> toIgnore, Set<String> toInclude) {
        super(src, toIgnore, toInclude);
        _nameTransformer = src._nameTransformer;
    }

    // @since 2.11.1
    protected UnwrappingBeanSerializer(UnwrappingBeanSerializer src,
            BeanPropertyWriter[] properties, BeanPropertyWriter[] filteredProperties) {
        super(src, properties, filteredProperties);
        _nameTransformer = src._nameTransformer;
    }

    /*
    /**********************************************************
    /* Life-cycle: factory methods, fluent factories
    /**********************************************************
     */

    @Override
    public JsonSerializer<Object> unwrappingSerializer(NameTransformer transformer) {
        // !!! 23-Jan-2012, tatu: Should we chain transformers?
        return new UnwrappingBeanSerializer(this, transformer);
    }

    @Override
    public boolean isUnwrappingSerializer() {
        return true; // sure is
    }

    @Override
    public BeanSerializerBase withObjectIdWriter(ObjectIdWriter objectIdWriter) {
        return new UnwrappingBeanSerializer(this, objectIdWriter);
    }

    @Override
    public BeanSerializerBase withFilterId(Object filterId) {
        return new UnwrappingBeanSerializer(this, _objectIdWriter, filterId);
    }

    @Override // @since 2.12
    protected BeanSerializerBase withByNameInclusion(Set<String> toIgnore, Set<String> toInclude) {
        return new UnwrappingBeanSerializer(this, toIgnore, toInclude);
    }

    @Override // @since 2.11.1
    protected BeanSerializerBase withProperties(BeanPropertyWriter[] properties,
            BeanPropertyWriter[] filteredProperties) {
        return new UnwrappingBeanSerializer(this, properties, filteredProperties);
    }

    /**
     * JSON Array output cannot be done if unwrapping operation is
     * requested; so implementation will simply return 'this'.
     */
    @Override
    protected BeanSerializerBase asArraySerializer() {
        return this;
    }
    
    /*
    /**********************************************************
    /* JsonSerializer implementation that differs between impls
    /**********************************************************
     */

    /**
     * Main serialization method that will delegate actual output to
     * configured
     * {@link BeanPropertyWriter} instances.
     */
    @Override
    public final void serialize(Object bean, JsonGenerator gen, SerializerProvider provider) throws IOException
    {
        gen.setCurrentValue(bean); // [databind#631]
        if (_objectIdWriter != null) {
            _serializeWithObjectId(bean, gen, provider, false);
            return;
        }
        if (_propertyFilterId != null) {
            serializeFieldsFiltered(bean, gen, provider);
        } else {
            serializeFields(bean, gen, provider);
        }
    }
    
    @Override
    public void serializeWithType(Object bean, JsonGenerator gen, SerializerProvider provider,
    		TypeSerializer typeSer) throws IOException
    {
        if (provider.isEnabled(SerializationFeature.FAIL_ON_UNWRAPPED_TYPE_IDENTIFIERS)) {
            provider.reportBadDefinition(handledType(),
                    "Unwrapped property requires use of type information: cannot serialize without disabling `SerializationFeature.FAIL_ON_UNWRAPPED_TYPE_IDENTIFIERS`");
        }
        gen.setCurrentValue(bean); // [databind#631]
        if (_objectIdWriter != null) {
            _serializeWithObjectId(bean, gen, provider, typeSer);
            return;
        }
        if (_propertyFilterId != null) {
            serializeFieldsFiltered(bean, gen, provider);
        } else {
            serializeFields(bean, gen, provider);
        }
    }

    /*
    /**********************************************************
    /* Standard methods
    /**********************************************************
     */

    @Override public String toString() {
        return "UnwrappingBeanSerializer for "+handledType().getName();
    }
}

⏎ com/fasterxml/jackson/databind/ser/impl/UnwrappingBeanSerializer.java

 

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