Need Code geändert werden Correct JSON von Java-Objekt zu erzeugen - Jackson

Question

Ich habe folgendes Ergebnis für die Abfrage select * from student where courseName = 'Science';

Ergebnisse:

student_id | name | points | course_name | course_id | 
+----------+--------+--------+---------------+-----------+ 
     1107| Matt | 3000 |  Science | 10  | 
|  1108| Charley| 12348 |  Science | 20  | 

2 rows in set, 2 warnings (0.00 sec) 

StudentsDetails.java:

@Entity(name = "com.StudentDetails") 
public class StudentDetails extends AbstractPersistable<Long> { 

    private long studentId; 
    private String name; 
    private long points; 
    private String courseName; 
    private long courseId; 

    public StudentDetails(long studentId, String name, long points, String courseName, long courseId) { 
    this.studentId = studentId; 
    this.name = name; 
    this.points = points; 
    this.courseName = courseName; 
    this.courseId = courseId; 
    } 

    public long getStudentId() { 
    return studentId; 
    } 

    public String getName() { 
    return name; 
    } 

    public long getPoints() { 
    return points; 
    } 

    public String getCourseName() { 
    return courseName; 
    } 

    public long getCourseId() { 
    return courseId; 
    } 
} 

I möchte eine JSON-Zeichenfolge erzeugen wie:

{ 
    "items": [ 
    { 
     "id": "123", 
     "students": [ 
     { 
      "name": 'Matt', 
      "points": 3000, 
      "course_name": 'Science', 
      "course_id": 10 
     } 
     ] 
    }, 
    { 
     "id": "324", 
     "students": [ 
     { 
      "name": 'Charley', 
      "points": 12348, 
      "course_name": Science, 
      "course_id": 20 
     } 
     ] 
    }, 
    { 
     "id": "898", 
     "error": { 
     "error_code": "500", 
     "error_message": "Details not found" 
     } 
    } 
    ] 
} 

derzeit 363.210

Ein Teil der Codeimplementierung wie folgt aussieht:

for (int i = 0; i < studentDetails.size(); i++) { 
     Details details = new Details(); 
     details.setName(studentDetails.get(i).getName()); 
     details.setPoints(studentDetails.get(i).getPoints()); 
     details.setCourseName(studentDetails.get(i).getCourseName()); 
     details.setCourseId(studentDetails.get(i).getCourseId()); 
     Listdetails.add(details); 
     item.setListDetails(Listdetails); 
    } 
    response = mapper.writeValueAsString(item); 

Above Code druckt die falsche JSON wie:

{"items":[{"id":"1107","details":[{"name": "Matt","points":3000,"course_name":"Science,"course_id":10},{"name":"Charley","points":12348,"course_name":"Science","course_id":20}]}]} 

statt

{"items":[{"id":"1107","details":[{"name": "Matt","points":3000,"course_name":"Science,"course_id":10}]},{"id":"1108","details":[{"name":"Charley","points":12348,"course_name":"Science","course_id":20}]} 

Bitte helfen Sie mir eine gute Umsetzung zu schreiben Code, um den richtigen JSON zu generieren. (Hinweis: Es ist nicht der richtige Code - nur eine Probe des echten Code)

Kurz gesagt: Ich möchte die Einträge aus der Datenbank-Tabelle lesen und machen es so:

items array -> [ 
      0th index : student_id, other related details (1107,['Matt',3000,'Science',10] 
      1st index : student_id, other related details(1108,['Charley',12348,'Science',20] 
       ] 

Answer 1

Zunächst alle, in Ihrem Json sollten Sie doppelte Anführungszeichen (") verwenden, damit das JSON gültig ist. Schließlich sollten Sie Jackson 2.x-Bibliothek verwenden. Dies ist eine sauberere Möglichkeit, json formatierte Daten zu bearbeiten und zu produzieren. Unten finden Sie a mögliche Umsetzung:

-----------------------------------com.example.Error.java------------------- 

package com.example; 

import com.fasterxml.jackson.annotation.JsonInclude; 
import com.fasterxml.jackson.annotation.JsonProperty; 
import com.fasterxml.jackson.annotation.JsonPropertyOrder; 

@JsonInclude(JsonInclude.Include.NON_NULL) 
@JsonPropertyOrder({ 
"error_code", 
"error_message" 
}) 
public class Error { 

@JsonProperty("error_code") 
public String errorCode; 
@JsonProperty("error_message") 
public String errorMessage; 

} 
-----------------------------------com.example.Example.java---------------- 

package com.example; 

import java.util.List; 
import com.fasterxml.jackson.annotation.JsonInclude; 
import com.fasterxml.jackson.annotation.JsonProperty; 
import com.fasterxml.jackson.annotation.JsonPropertyOrder; 

@JsonInclude(JsonInclude.Include.NON_NULL) 
@JsonPropertyOrder({ 
"items" 
}) 
public class Example { 

@JsonProperty("items") 
public List<Item> items = null; 

} 
-----------------------------------com.example.Item.java-------------------- 
package com.example; 

import java.util.List; 
import com.fasterxml.jackson.annotation.JsonInclude; 
import com.fasterxml.jackson.annotation.JsonProperty; 
import com.fasterxml.jackson.annotation.JsonPropertyOrder; 

@JsonInclude(JsonInclude.Include.NON_NULL) 
@JsonPropertyOrder({ 
"id", 
"students", 
"error" 
}) 
public class Item { 

@JsonProperty("id") 
public String id; 
@JsonProperty("students") 
public List<Student> students = null; 
@JsonProperty("error") 
public Error error; 

} 
-----------------------------------com.example.Student.java----------------- 

package com.example; 

import com.fasterxml.jackson.annotation.JsonInclude; 
import com.fasterxml.jackson.annotation.JsonProperty; 
import com.fasterxml.jackson.annotation.JsonPropertyOrder; 

@JsonInclude(JsonInclude.Include.NON_NULL) 
@JsonPropertyOrder({ 
"name", 
"points", 
"course_name", 
"course_id" 
}) 
public class Student { 

@JsonProperty("name") 
public String name; 
@JsonProperty("points") 
public Integer points; 
@JsonProperty("course_name") 
public String courseName; 
@JsonProperty("course_id") 
public Integer courseId; 

}