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

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

You can also browse Jackson Databind Source Code below:

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

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

import java.io.IOException;
import java.util.*;

import com.fasterxml.jackson.core.*;
import com.fasterxml.jackson.core.type.WritableTypeId;
import com.fasterxml.jackson.databind.*;
import com.fasterxml.jackson.databind.annotation.JacksonStdImpl;
import com.fasterxml.jackson.databind.jsonFormatVisitors.JsonArrayFormatVisitor;
import com.fasterxml.jackson.databind.jsonFormatVisitors.JsonFormatTypes;
import com.fasterxml.jackson.databind.jsontype.TypeSerializer;
import com.fasterxml.jackson.databind.ser.std.StaticListSerializerBase;

/**
 * Efficient implement for serializing {@link Collection}s that contain Strings.
 * The only complexity is due to possibility that serializer for {@link String}
 * may be overridde; because of this, logic is needed to ensure that the default
 * serializer is in use to use fastest mode, or if not, to defer to custom
 * String serializer.
 */
@JacksonStdImpl
@SuppressWarnings("serial")
public class StringCollectionSerializer
    extends StaticListSerializerBase<Collection<String>>
{
    public final static StringCollectionSerializer instance = new StringCollectionSerializer();

    /*
    /**********************************************************
    /* Life-cycle
    /**********************************************************
     */
    
    protected StringCollectionSerializer() {
        super(Collection.class);
    }

    protected StringCollectionSerializer(StringCollectionSerializer src,
            Boolean unwrapSingle)
    {
        super(src, unwrapSingle);
    }        

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

    @Override protected JsonNode contentSchema() {
        return createSchemaNode("string", true);
    }
    
    @Override
    protected void acceptContentVisitor(JsonArrayFormatVisitor visitor) throws JsonMappingException
    {
        visitor.itemsFormat(JsonFormatTypes.STRING);
    }

    /*
    /**********************************************************
    /* Actual serialization
    /**********************************************************
     */
    
    @Override
    public void serialize(Collection<String> value, JsonGenerator g,
            SerializerProvider provider) throws IOException
    {
        final int len = value.size();
        if (len == 1) {
            if (((_unwrapSingle == null) &&
                    provider.isEnabled(SerializationFeature.WRITE_SINGLE_ELEM_ARRAYS_UNWRAPPED))
                    || (_unwrapSingle == Boolean.TRUE)) {
                serializeContents(value, g, provider);
                return;
            }
        }
        g.writeStartArray(value, len);
        serializeContents(value, g, provider);
        g.writeEndArray();
    }

    @Override
    public void serializeWithType(Collection<String> value, JsonGenerator g,
            SerializerProvider provider, TypeSerializer typeSer)
        throws IOException
    {
        WritableTypeId typeIdDef = typeSer.writeTypePrefix(g,
                typeSer.typeId(value, JsonToken.START_ARRAY));
        g.setCurrentValue(value);
        serializeContents(value, g, provider);
        typeSer.writeTypeSuffix(g, typeIdDef);
    }

    private final void serializeContents(Collection<String> value, JsonGenerator g,
            SerializerProvider provider)
        throws IOException
    {
        int i = 0;

        try {
            for (String str : value) {
                if (str == null) {
                    provider.defaultSerializeNull(g);
                } else {
                    g.writeString(str);
                }
                ++i;
            }
        } catch (Exception e) {
            wrapAndThrow(provider, e, value, i);
        }
    }
}

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

 

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