与泛型数据绑定(Data Binding with Generics)
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小牛编辑
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2023-12-01
在简单的数据绑定中,我们使用了Map类,它使用String作为键,Object作为值对象。 相反,我们可以使用具体的java对象并将其类型转换为在JSON绑定中使用。
请考虑以下示例,其中包含UserData类,这是一个用于保存用户特定数据的类。
在C:\》Jackson_WORKSPACE创建名为C:\》Jackson_WORKSPACE的java类文件。
File: JacksonTester.java
import java.io.File;
import java.io.IOException;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;
public class JacksonTester {
public static void main(String args[]){
JacksonTester tester = new JacksonTester();
try {
ObjectMapper mapper = new ObjectMapper();
Map<String, UserData> userDataMap = new HashMap<String, UserData>();
UserData studentData = new UserData();
int[] marks = {1,2,3};
Student student = new Student();
student.setAge(10);
student.setName("Mahesh");
// JAVA Object
studentData.setStudent(student);
// JAVA String
studentData.setName("Mahesh Kumar");
// JAVA Boolean
studentData.setVerified(Boolean.FALSE);
// Array
studentData.setMarks(marks);
TypeReference ref = new TypeReference<Map<String,UserData>>() { };
userDataMap.put("studentData1", studentData);
mapper.writeValue(new File("student.json"), userDataMap);
//{
// "studentData1":
// {
// "student":
// {
// "name":"Mahesh",
// "age":10
// },
// "name":"Mahesh Kumar",
// "verified":false,
// "marks":[1,2,3]
// }
//}
userDataMap = mapper.readValue(new File("student.json"), ref);
System.out.println(userDataMap.get("studentData1").getStudent());
System.out.println(userDataMap.get("studentData1").getName());
System.out.println(userDataMap.get("studentData1").getVerified());
System.out.println(Arrays.toString(userDataMap.get("studentData1").getMarks()));
} catch (JsonParseException e) {
e.printStackTrace();
} catch (JsonMappingException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
class Student {
private String name;
private int age;
public Student(){}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String toString(){
return "Student [ name: "+name+", age: "+ age+ " ]";
}
}
class UserData {
private Student student;
private String name;
private Boolean verified;
private int[] marks;
public UserData(){}
public Student getStudent() {
return student;
}
public void setStudent(Student student) {
this.student = student;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Boolean getVerified() {
return verified;
}
public void setVerified(Boolean verified) {
this.verified = verified;
}
public int[] getMarks() {
return marks;
}
public void setMarks(int[] marks) {
this.marks = marks;
}
}
Verify the result
使用javac编译器编译类,如下所示:
C:\Jackson_WORKSPACE>javac JacksonTester.java
现在运行jacksonTester查看结果:
C:\Jackson_WORKSPACE>java JacksonTester
验证输出
Student [ name: Mahesh, age: 10 ]
Mahesh Kumar
false
[1, 2, 3]