Java操作JSON数据(2)

Gson是Google公司发布的一个开发源码的Java库，可用于将Java对象转换为JSON字符串，也可用于将JSON字符串转换为对应的Java对象。本介绍下Gson的基本使用方法，包括序列化和反序列化；文中所使用到的软件版本：Java 1.8.0_191、Gson 2.8.6。

1、引入依赖

1<dependency>
2  <groupId>com.google.code.gson</groupId>
3  <artifactId>gson</artifactId>
4  <version>2.8.6</version>
5</dependency>

2、序列化

1public static String serialize() {
2        MyBean bean = new MyBean();
3        bean.setS("测试字符串");
4        Calendar calendar = Calendar.getInstance();
5        calendar.add(Calendar.HOUR_OF_DAY, -1);
6        bean.setD(calendar.getTime());
7
8        List<MyBean> list = new ArrayList<MyBean>();
9        list.add(bean);
10        Map<String, List<MyBean>> map = new HashMap<String, List<MyBean>>();
11        map.put("data", list);
12
13        Gson gson = new GsonBuilder()
14                .serializeNulls() //序列化值为null的字段
15                .setDateFormat("yyyy-MM-dd HH:mm:ss") //设置日期格式
16                .excludeFieldsWithModifiers(Modifier.STATIC)//根据修饰符过滤字段
17                .create();
18        String result = gson.toJson(map);
19        System.out.println(result);
20        return result;
21    }

3、反序列化

1public static void deserialize() {
2        String s = serialize();
3        Gson gson = new GsonBuilder()
4                .setDateFormat("yyyy-MM-dd HH:mm:ss") //设置日期格式
5                .create();
6        Type type = new TypeToken<Map<String, List<MyBean>>>(){}.getType();
7        Map<String, List<MyBean>> map =  gson.fromJson(s, type);
8        System.out.println(map);
9        
10        //直接通过api获取相应数据
11        JsonElement element = JsonParser.parseString(s);
12        JsonArray data = element.getAsJsonObject().getAsJsonArray("data");
13        JsonObject bean = data.get(0).getAsJsonObject();
14        System.out.println(bean.get("s").getAsString());
15        //...
16    }

4、完整例子

1package com.inspur.demo.json;
2
3import java.lang.reflect.Modifier;
4import java.lang.reflect.Type;
5import java.util.ArrayList;
6import java.util.Calendar;
7import java.util.HashMap;
8import java.util.List;
9import java.util.Map;
10
11import com.google.gson.Gson;
12import com.google.gson.GsonBuilder;
13import com.google.gson.JsonArray;
14import com.google.gson.JsonElement;
15import com.google.gson.JsonObject;
16import com.google.gson.JsonParser;
17import com.google.gson.reflect.TypeToken;
18
19/**
20 * Gson操作JSON数据
21 */
22public class GsonCase {
23    /**
24     * 序列化
25     */
26    public static String serialize() {
27        MyBean bean = new MyBean();
28        bean.setS("测试字符串");
29        Calendar calendar = Calendar.getInstance();
30        calendar.add(Calendar.HOUR_OF_DAY, -1);
31        bean.setD(calendar.getTime());
32
33        List<MyBean> list = new ArrayList<MyBean>();
34        list.add(bean);
35        Map<String, List<MyBean>> map = new HashMap<String, List<MyBean>>();
36        map.put("data", list);
37
38        Gson gson = new GsonBuilder()
39                .serializeNulls() //序列化值为null的字段
40                .setDateFormat("yyyy-MM-dd HH:mm:ss") //设置日期格式
41                .excludeFieldsWithModifiers(Modifier.STATIC)//根据修饰符过滤字段
42                .create();
43        String result = gson.toJson(map);
44        System.out.println(result);
45        return result;
46    }
47
48    /**
49     * 反序列化
50     */
51    public static void deserialize() {
52        String s = serialize();
53        Gson gson = new GsonBuilder()
54                .setDateFormat("yyyy-MM-dd HH:mm:ss") //设置日期格式
55                .create();
56        Type type = new TypeToken<Map<String, List<MyBean>>>(){}.getType();
57        Map<String, List<MyBean>> map =  gson.fromJson(s, type);
58        System.out.println(map);
59        
60        //直接通过api获取相应数据
61        JsonElement element = JsonParser.parseString(s);
62        JsonArray data = element.getAsJsonObject().getAsJsonArray("data");
63        JsonObject bean = data.get(0).getAsJsonObject();
64        System.out.println(bean.get("s").getAsString());
65        //...
66    }
67    
68    public static void main(String[] args) {
69        serialize();
70        deserialize();
71    }
72
73}

GsonCase

1package com.inspur.demo.json;
2
3import java.util.Arrays;
4import java.util.Date;
5
6public class MyBean {
7    private String s = "字符串";
8    private String s2;
9    private String s3 = "字符串3";
10    private int i = 123;
11    private Integer i2;
12    private char c = '到';
13    private char[] c2 = new char[]{'a', 'b'};
14    private Date d = new Date();
15    private Date[] d2 = new Date[]{new Date(), new Date()};
16    public String getS() {
17        return s;
18    }
19    public void setS(String s) {
20        this.s = s;
21    }
22    public String getS2() {
23        return s2;
24    }
25    public void setS2(String s2) {
26        this.s2 = s2;
27    }
28    public String getS3() {
29        return s3;
30    }
31    public void setS3(String s3) {
32        this.s3 = s3;
33    }
34    public int getI() {
35        return i;
36    }
37    public void setI(int i) {
38        this.i = i;
39    }
40    public Integer getI2() {
41        return i2;
42    }
43    public void setI2(Integer i2) {
44        this.i2 = i2;
45    }
46    public char getC() {
47        return c;
48    }
49    public void setC(char c) {
50        this.c = c;
51    }
52    public char[] getC2() {
53        return c2;
54    }
55    public void setC2(char[] c2) {
56        this.c2 = c2;
57    }
58    public Date getD() {
59        return d;
60    }
61    public void setD(Date d) {
62        this.d = d;
63    }
64    public Date[] getD2() {
65        return d2;
66    }
67    public void setD2(Date[] d2) {
68        this.d2 = d2;
69    }
70    @Override
71    public String toString() {
72        return "MyBean [s=" + s + ", s2=" + s2 + ", s3=" + s3 + ", i=" + i + ", i2=" + i2 + ", c=" + c + ", c2="
73                + Arrays.toString(c2) + ", d=" + d + ", d2=" + Arrays.toString(d2) + "]";
74    }
75}

MyBean