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A framework for building RESTful web APIs.
/*
* Copyright 2016 Google Inc. All Rights Reserved.
*
* 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 com.google.api.server.spi.response;
import com.google.api.server.spi.ConfiguredObjectMapper;
import com.google.api.server.spi.Constant;
import com.google.api.server.spi.ServiceException;
import com.google.api.server.spi.SystemService;
import com.google.api.server.spi.config.model.ApiSerializationConfig;
import com.google.api.server.spi.types.DateAndTime;
import com.google.api.server.spi.types.SimpleDate;
import com.google.appengine.api.datastore.Blob;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.core.Version;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.ObjectWriter;
import com.fasterxml.jackson.databind.SerializerProvider;
import com.fasterxml.jackson.databind.module.SimpleModule;
import java.io.IOException;
import java.util.Collections;
import java.util.Date;
import java.util.HashMap;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Set;
import javax.servlet.http.HttpServletResponse;
/**
* Writes a result to a servlet response.
*/
public class ServletResponseResultWriter implements ResultWriter {
private static final Set WRITER_MODULES;
static {
Set modules = new LinkedHashSet<>();
modules.add(getWriteLongAsStringModule());
modules.add(getWriteDateAsStringModule());
modules.add(getWriteDateAndTimeAsStringModule());
modules.add(getWriteSimpleDateAsStringModule());
try {
// Attempt to load the Blob class, which may not exist outside of App Engine Standard.
ServletResponseResultWriter.class.getClassLoader()
.loadClass("com.google.appengine.api.datastore.Blob");
modules.add(getWriteBlobAsBase64Module());
} catch (ClassNotFoundException e) {
// Ignore this error, since we can function without the Blob deserializer.
}
WRITER_MODULES = Collections.unmodifiableSet(modules);
}
private final HttpServletResponse servletResponse;
private final ObjectWriter objectWriter;
public ServletResponseResultWriter(
HttpServletResponse servletResponse, ApiSerializationConfig serializationConfig) {
this(servletResponse, serializationConfig, false /* prettyPrint */);
}
public ServletResponseResultWriter(
HttpServletResponse servletResponse, ApiSerializationConfig serializationConfig,
boolean prettyPrint) {
this.servletResponse = servletResponse;
Set modules = new LinkedHashSet<>();
modules.addAll(WRITER_MODULES);
ObjectWriter objectWriter = ConfiguredObjectMapper.builder()
.apiSerializationConfig(serializationConfig)
.addRegisteredModules(modules)
.build()
.writer();
if (prettyPrint) {
objectWriter = objectWriter.with(new EndpointsPrettyPrinter());
}
this.objectWriter = objectWriter;
}
@Override
public void write(Object response) throws IOException {
if (response == null) {
write(HttpServletResponse.SC_NO_CONTENT, null, null);
} else {
write(HttpServletResponse.SC_OK, null,
writeValueAsString(ResponseUtil.wrapCollection(response)));
}
}
@Override
public void writeError(ServiceException e) throws IOException {
Map errors = new HashMap<>();
errors.put(Constant.ERROR_MESSAGE, e.getMessage());
write(e.getStatusCode(), e.getHeaders(),
writeValueAsString(errors));
}
protected void write(int status, Map headers, String content) throws IOException {
// write response status code
servletResponse.setStatus(status);
// write response headers
if (headers != null) {
for (Map.Entry entry : headers.entrySet()) {
servletResponse.addHeader(entry.getKey(), entry.getValue());
}
}
// write response body
if (content != null) {
servletResponse.setContentType(SystemService.MIME_JSON);
servletResponse.setContentLength(content.getBytes("UTF-8").length);
servletResponse.getWriter().write(content);
}
}
private static SimpleModule getWriteLongAsStringModule() {
JsonSerializer longSerializer = new JsonSerializer() {
@Override
public void serialize(Long value, JsonGenerator jgen, SerializerProvider provider)
throws IOException {
jgen.writeString(value.toString());
}
};
SimpleModule writeLongAsStringModule = new SimpleModule("writeLongAsStringModule",
new Version(1, 0, 0, null, null, null));
writeLongAsStringModule.addSerializer(Long.TYPE, longSerializer); // long (primitive)
writeLongAsStringModule.addSerializer(Long.class, longSerializer); // Long (class)
return writeLongAsStringModule;
}
private static SimpleModule getWriteDateAndTimeAsStringModule() {
JsonSerializer dateAndTimeSerializer = new JsonSerializer() {
@Override
public void serialize(DateAndTime value, JsonGenerator jgen, SerializerProvider provider)
throws IOException {
jgen.writeString(value.toRfc3339String());
}
};
SimpleModule writeDateAsStringModule = new SimpleModule("writeDateAsStringModule",
new Version(1, 0, 0, null, null, null));
writeDateAsStringModule.addSerializer(DateAndTime.class, dateAndTimeSerializer);
return writeDateAsStringModule;
}
private static SimpleModule getWriteSimpleDateAsStringModule() {
JsonSerializer simpleDateSerializer = new JsonSerializer() {
@Override
public void serialize(SimpleDate value, JsonGenerator jgen, SerializerProvider provider)
throws IOException {
jgen.writeString(
String.format("%04d-%02d-%02d", value.getYear(), value.getMonth(), value.getDay()));
}
};
SimpleModule writeSimpleDateAsModule = new SimpleModule("writeSimpleDateAsModule",
new Version(1, 0, 0, null, null, null));
writeSimpleDateAsModule.addSerializer(SimpleDate.class, simpleDateSerializer);
return writeSimpleDateAsModule;
}
private static SimpleModule getWriteDateAsStringModule() {
JsonSerializer dateSerializer = new JsonSerializer() {
@Override
public void serialize(Date value, JsonGenerator jgen, SerializerProvider provider)
throws IOException {
jgen.writeString(new com.google.api.client.util.DateTime(value).toStringRfc3339());
}
};
SimpleModule writeDateAsStringModule = new SimpleModule("writeDateAsStringModule",
new Version(1, 0, 0, null, null, null));
writeDateAsStringModule.addSerializer(Date.class, dateSerializer);
return writeDateAsStringModule;
}
private static SimpleModule getWriteBlobAsBase64Module() {
JsonSerializer dateSerializer = new JsonSerializer() {
@Override
public void serialize(Blob value, JsonGenerator jgen, SerializerProvider provider)
throws IOException {
byte[] bytes = value.getBytes();
jgen.writeBinary(bytes, 0, bytes.length);
}
};
SimpleModule writeBlobAsBase64Module = new SimpleModule("writeBlobAsBase64Module",
new Version(1, 0, 0, null, null, null));
writeBlobAsBase64Module.addSerializer(Blob.class, dateSerializer);
return writeBlobAsBase64Module;
}
// Writes a value as a JSON string and translates Jackson exceptions into IOException.
protected String writeValueAsString(Object value)
throws IOException {
try {
return objectWriter.writeValueAsString(value);
} catch (JsonProcessingException e) {
throw new IOException(e);
}
}
}