自定义GSON类型适配器

た入场券 2022-08-24 01:54 151阅读 0赞

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。**

**解决方案：定义自己的类型适配器。**

以下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 如下：

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;
 
 /**
 * 实现一个自定义的实行适配器
 * 
 * 基于Google GSON 实现JSON解析
 * 
 * 
 * @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());
 		}
 
 	}
 
 	/**
 	 * 测试
 	 * 
 	 * JSON->POJO
 	 * 
 	 * 
 	 * POJO->JSON
 	 * 
 	 * 
 	 * @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);
 			}
 		}
 
 	}
 }

运行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\}"\}