Java JSON数据处理技术 之 Gson
-
Maven依赖
com.google.code.gson gson 2.8.6 -
操作实体类：
public class Dept {
private Integer deptno;
private String dname;
private String loc;
public Dept() {
}
public Dept(Integer deptno, String dname, String loc) {
this.deptno = deptno;
this.dname = dname;
this.loc = loc;
}
public Integer getDeptno() {
return deptno;
}
public void setDeptno(Integer deptno) {
this.deptno = deptno;
}
public String getDname() {
return dname;
}
public void setDname(String dname) {
this.dname = dname;
}
public String getLoc() {
return loc;
}
public void setLoc(String loc) {
this.loc = loc;
}
@Override
public String toString() {
return "Dept{" +
"deptno=" + deptno +
", dname='" + dname + '\'' +
", loc='" + loc + '\'' +
'}';
}
}
public static void main(String[] args) {
Gson gson = new Gson();
Dept dept = new Dept(10, "RESEARCH", "NEWYORK");
//序列化
String json = gson.toJson(dept);
System.out.println(json);
//反序列化
Dept dept2 = gson.fromJson(json, Dept.class);
System.out.println(dept2);
}
public static void main(String[] args) {
Gson gson = new Gson();
String[] array = {"zhangsan","lisi","wanger","mazi"};
String json = gson.toJson(array);
System.out.println(json);
String[] res = gson.fromJson(json, String[].class);
for (String item : res) {
System.out.println(item);
}
}
- 代码一：
public static void main(String[] args) {
Gson gson = new Gson();
List list = new ArrayList();
Collections.addAll(list, "zhangsan", "lisi", "wanger", "mazi");
String json = gson.toJson(list);//序列化
System.out.println(json);
Type type = new TypeToken() {}.getType();
List res = gson.fromJson(json, type); //反序列化
res.forEach(System.out::println);
}
- 代码二：
public static void main(String[] args) {
Gson gson = new Gson();
List depts = new ArrayList();
depts.add(new Dept(10,"ACCOUNTING","NEWYORK"));
depts.add(new Dept(20,"RESEARCH","DALLAS"));
depts.add(new Dept(30,"SALES","CHICAGO"));
depts.add(new Dept(40,"OPERATIONS","BOSTON"));
String json = gson.toJson(depts);//序列化
System.out.println(json);
Type type = new TypeToken() {}.getType();
List res = gson.fromJson(json, type); //反序列化
res.forEach(System.out::println);
}
Set与List相同，示例略。
示例4：Map序列化与反序列化
```java
public static void main(String[] args) {
Gson gson = new Gson();
Map map = new HashMap();
map.put("accounting",new Dept(10,"ACCOUNTING","NEWYORK"));
map.put("research",new Dept(20,"RESEARCH","DALLAS"));
map.put("sales",new Dept(30,"SALES","CHICAGO"));
map.put("operations",new Dept(40,"OPERATIONS","BOSTON"));
String json = gson.toJson(map);//序列化
System.out.println(json);
Type type = new TypeToken() {}.getType();
Map res = gson.fromJson(json, type); //反序列化
res.forEach((k,v)-> System.out.println(k+" : "+v));
}
- 实体类：
public class Dept {
@Expose //参与序列化与反序列化
@SerializedName("no") //指定序列化反序列化的名称
private Integer deptno;
@Expose(serialize = false, deserialize = false)
//不参与序列化，也不参与反序列化
private String dname;
@Expose(serialize = false)
private String loc; //只参与反序列化
public Dept() {
}
public Dept(Integer deptno, String dname, String loc) {
this.deptno = deptno;
this.dname = dname;
this.loc = loc;
}
public Integer getDeptno() {
return deptno;
}
public void setDeptno(Integer deptno) {
this.deptno = deptno;
}
public String getDname() {
return dname;
}
public void setDname(String dname) {
this.dname = dname;
}
public String getLoc() {
return loc;
}
public void setLoc(String loc) {
this.loc = loc;
}
@Override
public String toString() {
return "Dept{" +
"deptno=" + deptno +
", dname='" + dname + '\'' +
", loc='" + loc + '\'' +
'}';
}
}
- 测试代码：
public static void main(String[] args) {
GsonBuilder builder = new GsonBuilder();
builder.excludeFieldsWithoutExposeAnnotation();
Gson gson = builder.create();
Dept dept = new Dept(10, "ACCOUNTING", "NEWYORK");
String json = gson.toJson(dept, Dept.class);
System.out.println(json);
String data = "{'deptno':40,'dname':'OPERATIONS','loc':'BOSTON'}";
Dept res = gson.fromJson(data, Dept.class);
System.out.println(res);
}
- 实体类
public class Stu {
private int id;
private Name name;
private Date birth;
public Stu() {
}
public Stu(int id, Name name, Date birth) {
this.id = id;
this.name = name;
this.birth = birth;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public Name getName() {
return name;
}
public void setName(Name name) {
this.name = name;
}
public Date getBirth() {
return birth;
}
public void setBirth(Date birth) {
this.birth = birth;
}
@Override
public String toString() {
return "Stu{" +
"id=" + id +
", name=" + name +
", birth=" + birth +
'}';
}
public static class Name{
private String firstName;
private String lastName;
public Name() {
}
public Name(String firstName, String lastName) {
this.firstName = firstName;
this.lastName = lastName;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
@Override
public String toString() {
return "Name{" +
"firstName='" + firstName + '\'' +
", lastName='" + lastName + '\'' +
'}';
}
}
}
- 测试代码
public static void main(String[] args) {
Gson gson1 = new Gson();
Stu stu = new Stu(1001, new Stu.Name("zhang", "san"), null);
String json1 = gson1.toJson(stu);//Gson默认情况下不会导出值为null的键
System.out.println(json1);
stu = new Stu(1001, new Stu.Name("zhang", "san"), new Date());
String json2 = gson1.toJson(stu); //内部类会序列化，日期格式默认
System.out.println(json2);
stu = new Stu(1001, null, new Date());
Gson gson = new GsonBuilder()
.serializeNulls() //序列化null
.setDateFormat("yyyy-MM-dd") // 设置日期时间格式，在序列化和反序化时均生效
.generateNonExecutableJson()//生成不可执行的Json，在最前面加上)]}'
.disableHtmlEscaping() //禁止转义html标签
.setPrettyPrinting() //格式化输出
.create();
String json3 = gson.toJson(stu);
System.out.println(json3);
}
