如何在 Java 中使用 Gson 的 @Since 注释?
javajsonobject oriented programmingprogramming
@Since 注释 可与 GsonBuilder 类的 setVersion() 方法一起使用。此注释可应用于 Java 类中的字段并接受浮点数作为参数。此参数表示字段已序列化的版本号。这同样适用于反序列化过程。
语法
@Documented
@Retention(value=RUNTIME)
@Target(value={FIELD,TYPE})
public @interface Since
示例
import com.google.gson.annotations.Since;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
public class GsonSinceAnnotationTest {
public static void main(String[] args) {
Employee emp = new Employee();
emp.setEmployeeName("Raja Ramesh");
emp.setEmployeeId(125);
emp.setEmployeeTechnology("Java");
emp.setEmploeeAddress("Hyderabad");
System.out.println("Since version 0.5");
GsonBuilder gsonBuilder = new GsonBuilder();
Gson gson = gsonBuilder.setPrettyPrinting().setVersion(0.5).create();
String jsonString = gson.toJson(emp);
System.out.println(jsonString);
System.out.println("Since version 1.0");
gsonBuilder = new GsonBuilder();
gson = gsonBuilder.setPrettyPrinting().setVersion(1.0).create();
jsonString = gson.toJson(emp);
System.out.println(jsonString);
System.out.println("Since version 1.1");
gsonBuilder = new GsonBuilder();
gson = gsonBuilder.setPrettyPrinting().setVersion(1.1).create();
jsonString = gson.toJson(emp);
System.out.println(jsonString);
}
}
// Employee class
class Employee {
private String empName;
private int empId;
@Since(1.0)
private String empTech;
@Since(1.1) private String empAddress;
public String getEmployeeName() {
return empName;
}
public void setEmployeeName(String empName) {
this.empName = empName;
}
public int getEmployeeId() {
return empId;
}
public void setEmployeeId(int empId) {
this.empId = empId;
}
public String getEmployeeTechnology() {
return empTech;
}
public void setEmployeeTechnology(String empTech) {
this.empTech = empTech;
}
public String getEmploeeAddress() {
return empAddress;
}
public void setEmploeeAddress(String empAddress) {
this.empAddress = empAddress;
}
}
输出
Since version 0.5
{
"empName": "Raja Ramesh",
"empId": 125
}
Since version 1.0
{
"empName": "Raja Ramesh",
"empId": 125,
"empTech": "Java"
}
Since version 1.1{
"empName": "Raja Ramesh",
"empId": 125,
"empTech": "Java",
"empAddress": "Hyderabad"
}
