List 转 json

package com.huarun.project.utils;

import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import net.sf.json.JSONArray;
import net.sf.json.JSONObject;

import com.fasterxml.jackson.core.JsonParser.Feature;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.google.common.collect.Maps;


/***
 * List 转 json 
 * 
 * @author Administrator
 *
 */

public class JsonMapper extends ObjectMapper{
	private static final long serialVersionUID = 1L;
	
	
	private static JsonMapper mapper;
	
	/**
	 * 允许单引号
	 * 允许不带引号的字段名称
	 */
	public JsonMapper enableSimple() {
		this.configure(Feature.ALLOW_SINGLE_QUOTES, true);
		this.configure(Feature.ALLOW_UNQUOTED_FIELD_NAMES, true);
		return this;
	}
	
	
	
	public static JsonMapper getInstance() {
		if (mapper == null){
			mapper = new JsonMapper().enableSimple();
		}
		return mapper;
	}
	
	
	
	/***
	 * 如果对象为Null,返回"null". 如果集合为空集合,返回"[]".
	 * 
	 * @param object
	 * @return
	 */
	public String toJson(Object object) {
		try {
			return this.writeValueAsString(object);
		} catch (IOException e) {
			return null;
		}
	}
	
	
	/**
	 * 测试 list 转 json
	 */
	public static void main(String[] args) {
		List<Map<String, Object>> list = new ArrayList<>();
		Map<String, Object> map = new HashMap<>();
		map.put("id", 1);
		map.put("pId", -1);
		map.put("name", "根节点");
		list.add(map);
		map = Maps.newHashMap();
		map.put("id", 2);
		map.put("pId", 1);
		map.put("name", "你好");
		map.put("open", true);
		list.add(map);
		Map<String, Object> map3 = new HashMap<>();
		map3.put("A1", 5);
		map3.put("B1", 5);
		map3.put("C1", 5);
		list.add(map3);
		//方法1
		String json = JsonMapper.getInstance().toJson(list);
		System.out.println(json);
		//方法2
		JSONArray subMsgs = JSONArray.fromObject(list);
		System.out.println(subMsgs);
		
		//JSONObject 测试
		JSONObject jsono = new JSONObject();
		jsono.put("age", "888");
		jsono.putAll(map);
		System.out.println(jsono);
		
		//Map 接收
		Map<String,Object> strmap=new JSONObject();
		strmap.put("group", "员工");
		strmap.put("from", "深圳");
		strmap.put("id", 33);
		System.out.println(strmap);

	        //json 字符串 转 json 对象
		JSONObject json1 = JSONObject.fromObject(json);
		System.out.println(json1);
	}
}