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/StringArraySerializer.java

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

import java.io.IOException;
import java.lang.reflect.Type;
import java.util.Objects;

import com.fasterxml.jackson.annotation.JsonFormat;

import com.fasterxml.jackson.core.JsonGenerator;

import com.fasterxml.jackson.databind.*;
import com.fasterxml.jackson.databind.annotation.JacksonStdImpl;
import com.fasterxml.jackson.databind.introspect.AnnotatedMember;
import com.fasterxml.jackson.databind.jsonFormatVisitors.JsonFormatTypes;
import com.fasterxml.jackson.databind.jsonFormatVisitors.JsonFormatVisitorWrapper;
import com.fasterxml.jackson.databind.jsontype.TypeSerializer;
import com.fasterxml.jackson.databind.ser.ContainerSerializer;
import com.fasterxml.jackson.databind.ser.ContextualSerializer;
import com.fasterxml.jackson.databind.ser.std.ArraySerializerBase;
import com.fasterxml.jackson.databind.type.TypeFactory;

/**
 * Standard serializer used for <code>String[]</code> values.
 */
@JacksonStdImpl
@SuppressWarnings("serial")
public class StringArraySerializer
    extends ArraySerializerBase<String[]>
    implements ContextualSerializer
{
    /* Note: not clean in general, but we are betting against
     * anyone re-defining properties of String.class here...
     */
    @SuppressWarnings("deprecation")
    private final static JavaType VALUE_TYPE = TypeFactory.defaultInstance().uncheckedSimpleType(String.class);

    public final static StringArraySerializer instance = new StringArraySerializer();

    /**
     * Value serializer to use, if it's not the standard one
     * (if it is we can optimize serialization a lot)
     */
    protected final JsonSerializer<Object> _elementSerializer;

    /*
    /**********************************************************
    /* Life-cycle
    /**********************************************************
     */
    
    protected StringArraySerializer() {
        super(String[].class);
        _elementSerializer = null;
    }

    @SuppressWarnings("unchecked")
    public StringArraySerializer(StringArraySerializer src,
            BeanProperty prop, JsonSerializer<?> ser, Boolean unwrapSingle) {
        super(src, prop, unwrapSingle);
        _elementSerializer = (JsonSerializer<Object>) ser;
    }

    @Override
    public JsonSerializer<?> _withResolved(BeanProperty prop, Boolean unwrapSingle) {
        return new StringArraySerializer(this, prop, _elementSerializer, unwrapSingle);
    }

    /**
     * Strings never add type info; hence, even if type serializer is suggested,
     * we'll ignore it...
     */
    @Override
    public ContainerSerializer<?> _withValueTypeSerializer(TypeSerializer vts) {
        return this;
    }

    /*
    /**********************************************************
    /* Post-processing
    /**********************************************************
     */
    
    @Override
    public JsonSerializer<?> createContextual(SerializerProvider provider,
            BeanProperty property)
        throws JsonMappingException
    {
        /* 29-Sep-2012, tatu: Actually, we need to do much more contextual
         *    checking here since we finally know for sure the property,
         *    and it may have overrides
         */
        JsonSerializer<?> ser = null;

        // First: if we have a property, may have property-annotation overrides
        if (property != null) {
            final AnnotationIntrospector ai = provider.getAnnotationIntrospector();
            AnnotatedMember m = property.getMember();
            if (m != null) {
                Object serDef = ai.findContentSerializer(m);
                if (serDef != null) {
                    ser = provider.serializerInstance(m, serDef);
                }
            }
        }
        // but since formats have both property overrides and global per-type defaults,
        // need to do that separately
        Boolean unwrapSingle = findFormatFeature(provider, property, String[].class,
                JsonFormat.Feature.WRITE_SINGLE_ELEM_ARRAYS_UNWRAPPED);
        if (ser == null) {
            ser = _elementSerializer;
        }
        // May have a content converter
        ser = findContextualConvertingSerializer(provider, property, ser);
        if (ser == null) {
            ser = provider.findContentValueSerializer(String.class, property);
        }
        // Optimization: default serializer just writes String, so we can avoid a call:
        if (isDefaultSerializer(ser)) {
            ser = null;
        }
        // note: will never have TypeSerializer, because Strings are "natural" type
        if ((ser == _elementSerializer) && (Objects.equals(unwrapSingle, _unwrapSingle))) {
            return this;
        }
        return new StringArraySerializer(this, property, ser, unwrapSingle);
    }

    /*
    /**********************************************************
    /* Simple accessors
    /**********************************************************
     */

    @Override
    public JavaType getContentType() {
        return VALUE_TYPE;
    }

    @Override
    public JsonSerializer<?> getContentSerializer() {
        return _elementSerializer;
    }
    
    @Override
    public boolean isEmpty(SerializerProvider prov, String[] value) {
        return (value.length == 0);
    }

    @Override
    public boolean hasSingleElement(String[] value) {
        return (value.length == 1);
    }
    
    /*
    /**********************************************************
    /* Actual serialization
    /**********************************************************
     */
    
    @Override
    public final void serialize(String[] value, JsonGenerator gen, SerializerProvider provider)
        throws IOException
    {
        final int len = value.length;
        if (len == 1) {
            if (((_unwrapSingle == null) &&
                    provider.isEnabled(SerializationFeature.WRITE_SINGLE_ELEM_ARRAYS_UNWRAPPED))
                    || (_unwrapSingle == Boolean.TRUE)) {
                serializeContents(value, gen, provider);
                return;
            }
        }
        gen.writeStartArray(value, len);
        serializeContents(value, gen, provider);
        gen.writeEndArray();
    }
    
    @Override
    public void serializeContents(String[] value, JsonGenerator gen, SerializerProvider provider)
        throws IOException
    {
        final int len = value.length;
        if (len == 0) {
            return;
        }
        if (_elementSerializer != null) {
            serializeContentsSlow(value, gen, provider, _elementSerializer);
            return;
        }
        for (int i = 0; i < len; ++i) {
            String str = value[i];
            if (str == null) {
                gen.writeNull();
            } else {
                gen.writeString(value[i]);
            }
        }
    }

    private void serializeContentsSlow(String[] value, JsonGenerator gen, SerializerProvider provider, JsonSerializer<Object> ser)
        throws IOException
    {
        for (int i = 0, len = value.length; i < len; ++i) {
            String str = value[i];
            if (str == null) {
                provider.defaultSerializeNull(gen);
            } else {
                ser.serialize(value[i], gen, provider);
            }
        }
    }

    @Override
    public JsonNode getSchema(SerializerProvider provider, Type typeHint) {
        return createSchemaNode("array", true).set("items", createSchemaNode("string"));
    }
    
    @Override
    public void acceptJsonFormatVisitor(JsonFormatVisitorWrapper visitor, JavaType typeHint) throws JsonMappingException
    {
        visitArrayFormat(visitor, typeHint, JsonFormatTypes.STRING);
    }
}

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

 

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