自己定义GSON类型适配器

Exception in thread "main"
java.lang.RuntimeException: No-args constructor for class java.sql.Timestamp does not exist. Register an InstanceCreator with Gson for this type to fix this problem.

#关于使用Google GSON 实现Json协议字符协议序列化和反序列化 时间戳到Timestame类型转换失败问题。

解决方式：定义自己的类型适配器。

下面代码演示了两个问题：

1.解决上面说的时间戳到Timestame类型互转问题。

2.扩展了一个基于HTTP协议URL字符串解析到POJO HttpProtocol 的互转。

Code 例如以下：

package com.kevin.luan.service;

import java.lang.reflect.Type;
import java.sql.Timestamp;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.JsonDeserializationContext;
import com.google.gson.JsonDeserializer;
import com.google.gson.JsonElement;
import com.google.gson.JsonParseException;
import com.google.gson.JsonPrimitive;
import com.google.gson.JsonSerializationContext;
import com.google.gson.JsonSerializer;

/**
 * 实现一个自己定义的实行适配器
 * <p>
 * 基于Google GSON 实现JSON解析
 * </p>
 *
 * @author kevin LUAN
 *
 */
public class GsonTypeAdapterDemo {
	public static void main(String[] args) {
		Gson gson = new GsonBuilder().registerTypeAdapter(Timestamp.class, new TimestampAdapter()).registerTypeAdapter(HttpProtocol.class, new HttpProtocolAdapter()).create();
		String json = "{\"price\":\"1.1001\",\"times\":\"" + System.currentTimeMillis() + "\",\"protocol\":\"http://www.koudai.com/abc/test.do?url=abc\"}";
		Test pojo = gson.fromJson(json, Test.class);
		System.out.println("JSON TO POJO:" + pojo);
		json = gson.toJson(pojo);
		System.err.println("POJO TO JSON:" + json);
	}

	/**
	 * 实现一个类型适配器(TypeAdapter)
	 *
	 * @author kevin LUAN
	 *
	 */
	public static class TimestampAdapter implements JsonSerializer<Timestamp>, JsonDeserializer<Timestamp> {

		@Override
		public Timestamp deserialize(JsonElement json, Type type, JsonDeserializationContext context) throws JsonParseException {
			if (json != null) {
				try {
					return new Timestamp(json.getAsLong());
				} catch (JsonParseException e) {
					throw e;
				}
			}
			return null;
		}

		@Override
		public JsonElement serialize(Timestamp value, Type type, JsonSerializationContext context) {
			if (value != null) {
				return new JsonPrimitive(value.getTime());
			}
			return null;
		}

	}

	/**
	 * 基于HttpProtocol的类型适配器
	 *
	 * @author kevin LUAN
	 *
	 */
	public static class HttpProtocolAdapter implements JsonSerializer<HttpProtocol>, JsonDeserializer<HttpProtocol> {

		@Override
		public HttpProtocol deserialize(JsonElement json, Type arg1, JsonDeserializationContext arg2) throws JsonParseException {
			if (json == null) {
				return null;
			} else {
				try {
					return new HttpProtocol(json.toString());
				} catch (Exception e) {
					e.printStackTrace();
					return null;
				}
			}
		}

		@Override
		public JsonElement serialize(HttpProtocol src, Type arg1, JsonSerializationContext arg2) {
			return new JsonPrimitive(src.toString());
		}

	}

	/**
	 * 測试
	 * <p>
	 * JSON->POJO
	 * </p>
	 * <p>
	 * POJO->JSON
	 * </p>
	 *
	 * @author kevin LUAN
	 *
	 */
	public static class Test {
		private Float price = 1.0f;
		private Timestamp times;
		private HttpProtocol protocol;

		@Override
		public String toString() {
			return "price:" + price + "|times:" + times + "|protocl:" + protocol + "";
		}

	}

	/**
	 * HTTP协议POJO
	 *
	 * @author kevin LUAN
	 *
	 */
	public static class HttpProtocol {
		private String protocol;
		private String host;
		private int port = -1;
		private String uri;
		private String paramQuery;

		@Override
		public String toString() {
			return protocol + "://" + host + ":" + port + uri + "?" + paramQuery + "}";
		}

		public HttpProtocol(String value) {
			if (value.startsWith("\"") && value.endsWith("\"")) {
				value = value.substring(1, value.length() - 1);
			}
			parserProtocol(value);
		}

		private void parserProtocol(String value) {
			int endIndex = value.indexOf("://");
			if (endIndex != -1) {
				protocol = value.substring(0, endIndex);
				parserHost(value, endIndex + 3);
			}
		}

		private void parserHost(String value, int startIndex) {
			int endIndex = value.indexOf("/", startIndex);
			if (endIndex != -1) {
				host = value.substring(startIndex, endIndex);
				splitHostPort();
				parserUri(value, endIndex);
			} else {
				host = value.substring(startIndex);
				splitHostPort();
			}
		}

		private void splitHostPort() {
			if (host.indexOf(":") != -1) {
				String host_port[] = host.split(":");
				host = host_port[0];
				port = Integer.parseInt(host_port[1]);
			} else {
				port = 80;
			}
		}

		private void parserUri(String value, int startIndex) {
			if (value.indexOf("?", startIndex) == -1) {
				uri = value.substring(startIndex);
			} else {
				int endIndex = value.indexOf("?", startIndex);
				uri = value.substring(startIndex, endIndex);
				parserQuery(value, endIndex);
			}
		}

		private void parserQuery(String value, int startIndex) {
			if (value.indexOf("?", startIndex) != -1) {
				int paramQueryIndex = value.indexOf("?", startIndex);
				paramQuery = value.substring(paramQueryIndex + 1);
			}
		}

	}
}

执行Main结果：

JSON TO POJO:price:1.1001|times:2014-06-22 13:06:54.138|protocl:http://www.koudai.com:80/abc/test.do?url=abc}

POJO TO JSON:{"price":1.1001,"times":1403413614138,"protocol":"http://www.koudai.com:80/abc/test.do?url\u003dabc}"}