在Java中使用Gson的自定义实例创建者？
在与Java对象之间来回解析JSON字符串时，默认情况下，Gson尝试通过调用默认构造函数来创建Java类的实例。如果Java类不包含默认构造函数，或者我们想在创建Java对象时进行一些初始配置，则需要创建并注册自己的实例创建者。
我们可以使用InstanceCreator 接口 在Gson中创建自定义实例创建者，并且需要实现createInstance（Typetype）方法。
语法
T createInstance(Type type)
示例
import java.lang.reflect.Type;
import com.google.gson.*;
public class CustomInstanceCreatorTest {
public static void main(String args[]) {
GsonBuilder gsonBuilder = new GsonBuilder();
gsonBuilder.registerTypeAdapter(Course.class, new CourseCreator());
Gson gson = gsonBuilder.create();
String jsonString = "{'course1':'Core Java', 'course2':'Advanced Java'}";
Course course = gson.fromJson(jsonString, Course.class);
System.out.println(course);
}
}
//课程课程
class Course {
private String course1;
private String course2;
private String technology;
public Course(String technology) {
this.technology = technology;
}
public void setCourse1(String course1) {
this.course1 = course1;
}
public void setCourse2(String course2) {
this.course2 = course2;
}
public String getCourse1() {
return course1;
}
public String getCourse2() {
return course1;
}
public void setTechnology(String technology) {
this.technology = technology;
}
public String getTechnology() {
return technology;
}
public String toString() {
return "Course[ " +
"course1 = " + course1 +
", course2 = " + course2 +
", technology = " + technology +
" ]";
}
}
//CourseCreator类
class CourseCreator implements InstanceCreator {
@Override
public Course createInstance(Type type) {
Course course = new Course("Java");
return course;
}
}输出结果
Course[ course1 = Core Java, course2 = Advanced Java, technology = Java ]