org.springframework.data.repository.init.Jackson2ResourceReader.java Source code

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Here is the source code for org.springframework.data.repository.init.Jackson2ResourceReader.java

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/*
 * Copyright 2013-2014 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.springframework.data.repository.init;

import static com.fasterxml.jackson.databind.DeserializationFeature.*;

import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import org.springframework.core.io.Resource;
import org.springframework.util.ClassUtils;

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;

/**
 * A {@link ResourceReader} using Jackson to read JSON into objects.
 * 
 * @author Oliver Gierke
 * @since 1.6
 */
public class Jackson2ResourceReader implements ResourceReader {

    private static final String DEFAULT_TYPE_KEY = "_class";
    private static final ObjectMapper DEFAULT_MAPPER = new ObjectMapper();

    static {
        DEFAULT_MAPPER.configure(FAIL_ON_UNKNOWN_PROPERTIES, false);
    }

    private final ObjectMapper mapper;
    private String typeKey = DEFAULT_TYPE_KEY;

    /**
     * Creates a new {@link Jackson2ResourceReader}.
     */
    public Jackson2ResourceReader() {
        this(DEFAULT_MAPPER);
    }

    /**
     * Creates a new {@link Jackson2ResourceReader} using the given {@link ObjectMapper}.
     * 
     * @param mapper
     */
    public Jackson2ResourceReader(ObjectMapper mapper) {
        this.mapper = mapper == null ? DEFAULT_MAPPER : mapper;
    }

    /**
     * Configures the JSON document's key to lookup the type to instantiate the object. Defaults to
     * {@link Jackson2ResourceReader#DEFAULT_TYPE_KEY}.
     * 
     * @param typeKey
     */
    public void setTypeKey(String typeKey) {
        this.typeKey = typeKey;
    }

    /*
     * (non-Javadoc)
     * @see org.springframework.data.repository.init.ResourceReader#readFrom(org.springframework.core.io.Resource, java.lang.ClassLoader)
     */
    public Object readFrom(Resource resource, ClassLoader classLoader) throws Exception {

        InputStream stream = resource.getInputStream();
        JsonNode node = mapper.readerFor(JsonNode.class).readTree(stream);

        if (node.isArray()) {

            Iterator<JsonNode> elements = node.elements();
            List<Object> result = new ArrayList<>();

            while (elements.hasNext()) {
                JsonNode element = elements.next();
                result.add(readSingle(element, classLoader));
            }

            return result;
        }

        return readSingle(node, classLoader);
    }

    /**
     * Reads the given {@link JsonNode} into an instance of the type encoded in it using the configured type key.
     * 
     * @param node must not be {@literal null}.
     * @param classLoader
     * @return
     */
    private Object readSingle(JsonNode node, ClassLoader classLoader) throws IOException {

        JsonNode typeNode = node.findValue(typeKey);
        String typeName = typeNode == null ? null : typeNode.asText();

        Class<?> type = ClassUtils.resolveClassName(typeName, classLoader);

        return mapper.readerFor(type).readValue(node);
    }
}