Protostuff自定义序列化（Delegate）解析

背景
在使用Protostuff进行序列化的时候，不幸地遇到了一个问题，就是Timestamp作为字段的时候，转换出现问题，通过Protostuff转换后的结果都是1970-01-01 08:00:00，这就造成了Timestamp不能够序列化。于是Google了一番，得知可以用Delegate来解决这个问题。

原来的代码
ProtobufferCodec类

import java.lang.reflect.Constructor;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import io.protostuff.LinkedBuffer;
import io.protostuff.ProtostuffIOUtil;
import io.protostuff.Schema;
import io.protostuff.runtime.RuntimeSchema;

public class ProtobufferCodec implements Codec {

private static Map<Class<?>, Schema<?>> cachedSchema = new ConcurrentHashMap<>();

public ProtobufferCodec() {

}

@Override
public short getId() {
return Codecs.PROTOBUFFER_CODEC;
}

@SuppressWarnings("unchecked")
private static <T> Schema<T> getSchema(Class<T> cls) {
Schema<T> schema = (Schema<T>) cachedSchema.get(cls);
if (schema == null) {
schema = RuntimeSchema.createFrom(cls);
if (schema != null) {
cachedSchema.put(cls, schema);
}
}
return schema;
}

@Override
public <T> byte[] encode(T obj) {
if (obj == null) {
return null;
}
Class<T> cls = (Class<T>) obj.getClass();
LinkedBuffer buffer = LinkedBuffer.allocate(LinkedBuffer.DEFAULT_BUFFER_SIZE);
try {
Schema<T> schema = getSchema(cls);
byte[] bytes = ProtostuffIOUtil.toByteArray(obj, schema, buffer);
return bytes;
} catch (Exception e) {
throw new IllegalStateException(e.getMessage(), e);
} finally {
buffer.clear();
}
}

@Override
public <T> T decode(byte[] bytes, Class<T> clazz) {
if (bytes == null || bytes.length == 0) {
return null;
}
try {
Constructor<T> constructor = clazz.getConstructor();
constructor.setAccessible(true);
T message = constructor.newInstance();
Schema<T> schema = getSchema(clazz);
ProtostuffIOUtil.mergeFrom(bytes, message, schema);
return message;
} catch (Exception e) {
throw new IllegalStateException(e.getMessage(), e);
}
}

}
Codec接口
/**
* 编解码器
* @author jiujie
* @version $Id: Codec.java, v 0.1 2016年3月31日 上午11:39:14 jiujie Exp $
*/
public interface Codec {

/**
* 编解码器ID，用于标识编解码器
* @author jiujie
* 2016年3月31日 上午11:38:39
* @return
*/
public short getId();

/**
* 把对象数据结构编码成一个DataBuffer
* @param <T>
*/
public <T> byte[] encode(T obj);

/**
* 把DataBuffer解包构造一个对象
* @param <T>
*/
public <T> T decode(byte[] bytes, Class<T> clazz);

修改后的代码
import java.sql.Timestamp;
import java.util.concurrent.ConcurrentHashMap;

import io.protostuff.LinkedBuffer;
import io.protostuff.ProtostuffIOUtil;
import io.protostuff.Schema;
import io.protostuff.runtime.DefaultIdStrategy;
import io.protostuff.runtime.Delegate;
import io.protostuff.runtime.RuntimeEnv;
import io.protostuff.runtime.RuntimeSchema;

/**
* ProtoBuffer编解码
* @author jiujie
* @version $Id: ProtobufferCodec.java, v 0.1 2016年7月20日 下午1:52:41 jiujie Exp $
*/
public class ProtobufferCodec implements Codec {

/** 时间戳转换Delegate，解决时间戳转换后错误问题 @author jiujie 2016年7月20日 下午1:52:25 */
private final static Delegate<Timestamp> TIMESTAMP_DELEGATE = new TimestampDelegate();

private final static DefaultIdStrategy idStrategy = ((DefaultIdStrategy) RuntimeEnv.ID_STRATEGY);

private final static ConcurrentHashMap<Class<?>, Schema<?>> cachedSchema = new ConcurrentHashMap<>();

static {
idStrategy.registerDelegate(TIMESTAMP_DELEGATE);
}

public ProtobufferCodec() {
}

@Override
public short getId() {
return Codecs.PROTOBUFFER_CODEC;
}

@SuppressWarnings("unchecked")
public static <T> Schema<T> getSchema(Class<T> clazz) {
Schema<T> schema = (Schema<T>) cachedSchema.get(clazz);
if (schema == null) {
schema = RuntimeSchema.createFrom(clazz, idStrategy);
cachedSchema.put(clazz, schema);
}
return schema;
}

@Override
public <T> byte[] encode(T obj) {
if (obj == null) {
return null;
}
@SuppressWarnings("unchecked")
Class<T> cls = (Class<T>) obj.getClass();
LinkedBuffer buffer = LinkedBuffer.allocate(LinkedBuffer.DEFAULT_BUFFER_SIZE);
try {
Schema<T> schema = getSchema(cls);
byte[] bytes = ProtostuffIOUtil.toByteArray(obj, schema, buffer);
return bytes;
} catch (Exception e) {
throw new IllegalStateException(e.getMessage(), e);
} finally {
buffer.clear();
}
}

@Override
public <T> T decode(byte[] bytes, Class<T> clazz) {
if (bytes == null || bytes.length == 0) {
return null;
}
try {
Schema<T> schema = getSchema(clazz);
//改为由Schema来实例化解码对象，没有构造函数也没有问题
T message = schema.newMessage();
ProtostuffIOUtil.mergeFrom(bytes, message, schema);
return message;
} catch (Exception e) {
throw new IllegalStateException(e.getMessage(), e);
}
}

}

TimestampDelegate类

import java.io.IOException;
import java.sql.Timestamp;

import io.protostuff.Input;
import io.protostuff.Output;
import io.protostuff.Pipe;
import io.protostuff.WireFormat.FieldType;
import io.protostuff.runtime.Delegate;

/**
* protostuff timestamp Delegate
* @author jiujie
* @version $Id: TimestampDelegate.java, v 0.1 2016年7月20日 下午2:08:11 jiujie Exp $
*/
public class TimestampDelegate implements Delegate<Timestamp> {

public FieldType getFieldType() {
return FieldType.FIXED64;
}

public Class<?> typeClass() {
return Timestamp.class;
}

public Timestamp readFrom(Input input) throws IOException {
return new Timestamp(input.readFixed64());
}

public void writeTo(Output output, int number, Timestamp value,
boolean repeated) throws IOException {
output.writeFixed64(number, value.getTime(), repeated);
}

public void transfer(Pipe pipe, Input input, Output output, int number,
boolean repeated) throws IOException {
output.writeFixed64(number, input.readFixed64(), repeated);
}

}

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原文链接：https://blog.csdn.net/connect_me/article/details/51970201