/*
* 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.reader(JsonNode.class).readTree(stream);
if (node.isArray()) {
Iterator<JsonNode> elements = node.elements();
List<Object> result = new ArrayList<Object>();
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.reader(type).readValue(node);
}
}