GSON 多层Map剥离 - 码农教程

工作中遇到一个问题，我们提供给外包方的 json 无法Decode 。

一段简单 JSON 字符串，字符串如下。

String json= "{"0":{"id":"2","category_id":"1","title":"Test2","author":"","ctime":"2016-03-05 11:59:56"},"1":{"id":"1","category_id":"1","title":"Test1","author":"u6d4bu8bd5","ctime":"2016-03-05 11:57:30"},"pages":{"count":2,"first":0,"last":0,"before":0,"current":0,"next":0,"total":0}}";

对方话费了大量时间解决不了问题。后来说请了 “新浪” 高手过来（让我想到周星驰电影，他们请来大内高手高手高高手）。看后也无能为力，说我们JSON 字符串不符合JSON标准规范。

我无语！啥也不说了，帮你们写一个例子吧。

12.2. com.google.gson

https://github.com/google/gson

首先看看怎么剥离一层Map

		<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>sender</groupId>
	<artifactId>sender</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>Sender</name>
	<description>EDM</description>

	<dependencies>
		<dependency>
			<groupId>com.rabbitmq</groupId>
			<artifactId>amqp-client</artifactId>
			<version>3.6.0</version>
		</dependency>
		<dependency>
			<groupId>com.google.code.gson</groupId>
			<artifactId>gson</artifactId>
			<version>2.6.2</version>
			<scope>compile</scope>
		</dependency>
	</dependencies>

</project>

		package io.github.netkiller;

import java.util.HashMap;
import java.util.Map;

import com.google.gson.*;

public class GsonTest {

	public static void main(String[] args) {
		// TODO Auto-generated method stub

		Gson gson = new Gson();
		String json = "{"k1":"v1","k2":"v2"}";
		Map<String, String> map = new HashMap<String, String>();
		map = (Map<String, String>) gson.fromJson(json, map.getClass());
		System.out.println(map.get("k1"));
	}

}

12.2.1. 多层 Map 剥离

		Gson gson = new Gson();
		String json= "{"0":{"id":"2","category_id":"1","title":"Test2","author":"","ctime":"2016-03-05 11:59:56"},"1":{"id":"1","category_id":"1","title":"Test1","author":"u6d4bu8bd5","ctime":"2016-03-05 11:57:30"},"pages":{"count":2,"first":0,"last":0,"before":0,"current":0,"next":0,"total":0}}";
		Map<String, Map> map = new HashMap<String, Map>();
		
		map = (Map<String, Map>) gson.fromJson(json, map.getClass());
		System.out.println(map.get("1").get("title"));
		System.out.println(map.get("pages").get("count"));

以上例子节选自《Netkiller Java 手札》