Jackson将json string转为Object，org.json读取json数组

ilovena 2017-12-11 原文

　　从json文件读取json string或者自定义json string，将其转为object。下面采用的object为map，根据map读取json的某个数据，可以读取第一级的数据name，后来发现想转成JsonArray读取”red“时没撤了，只好用了其他方法。

　最后用org.json包解决了（readJsonArray函数），有空再看看有没有更好的办法。

JSON文件如下：

1 {
2     "name":"name",
3     "id":"id",
4     "color":[
5         {"red":"red","blue":"blue"},
6         {"white":"white"}
7     ]
8 }

代码如下：

 1 package com;
 2 
 3 import org.codehaus.jackson.map.ObjectMapper;
 4 import org.json.JSONArray;
 5 import org.json.JSONObject;
 6 import org.slf4j.Logger;
 7 import org.slf4j.LoggerFactory;
 8 
 9 import java.io.*;
10 import java.util.Map;
11 
12 /**
13  * Hello world!
14  *
15  */
16 public class JsonAnalysis
17 {
18     private static final Logger LOG = LoggerFactory.getLogger(JsonAnalysis.class);
19     public static void main(String[] args) throws FileNotFoundException {
20         String jsonString = "{\"address\":\"address\",\"name\":\"name\",\"id\":\"1\",\"email\":\"email\"}";
21         FileReader fileReader = new FileReader("E:\\JsonAnalysis\\src\\test.json");
22         String fileString = readFile(fileReader);
23         //Json字符串转java对象,比如转为Map对象读取其中数据
24         Map map = null;
25         Map mapFile = null;
26         try {
27             map = readValue(jsonString, Map.class);
28             mapFile = readValue(fileString, Map.class);
29         } catch (Exception e) {
30             e.printStackTrace();
31             LOG.error("ReadValue occur exception when switch json string to map");
32         }
33         System.out.println(map != null ? map.get("id") : null);
34         if (mapFile==null){
35             LOG.info("Json map form file is empty");
36             return;
37         }
38         System.out.println(mapFile.get("name"));
39 
40         try {
41             readJsonArray(fileString);
42         } catch (Exception e) {
43             e.printStackTrace();
44         }
45     }
46     //Json string to object
47     private static <T> T readValue(String jsonStr, Class<T> valueType) throws Exception{
48         ObjectMapper objectMapper = new ObjectMapper();
49         try {
50 //            Object object = objectMapper.readValue(jsonStr,Object.class);
51             return objectMapper.readValue(jsonStr,valueType);
52         } catch (IOException e) {
53             e.printStackTrace();
54         }
55         return null;
56     }
57     //Read file and to string
58     private static String readFile(FileReader fileReader){
59         BufferedReader bufferedReader = new BufferedReader(fileReader);
60         StringBuilder fileStr = new StringBuilder();
61         try {
62             String eachLine;
63             while ((eachLine=bufferedReader.readLine())!=null){
64                 fileStr.append(eachLine);
65             }
66             return fileStr.toString();
67         } catch (IOException e1) {
68             e1.printStackTrace();
69             LOG.error("Occur exception when read file,file={}",fileReader);
70             return null;
71         }
72     }
73     //根据json string 获取json array,读取数据（ 注意该部分引用的是org.json 包）
74     private static void readJsonArray(String jsonStr) throws Exception {
75         JSONObject jsonObject = new JSONObject(jsonStr);
76         JSONArray jsonArray = jsonObject.getJSONArray("color");
77 
78         JSONObject jsonObject1 = jsonArray.getJSONObject(0);
79         System.out.println(jsonObject1.get("red"));
80     }
81 }