优化Spring Boot REST API响应：避免JPA不必要关联数据返回

// Student.java
package com.example.demo.entity;

import com.fasterxml.jackson.annotation.JsonIgnore;
import jakarta.persistence.*;
import java.util.HashSet;
import java.util.Set;

@Entity
public class Student {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;

    // 假设 Student 与 Course 之间是多对多关系
    @ManyToMany(fetch = FetchType.LAZY)
    @JoinTable(
        name = "student_course",
        joinColumns = @JoinColumn(name = "student_id"),
        inverseJoinColumns = @JoinColumn(name = "course_id")
    )
    @JsonIgnore // 在这里添加 @JsonIgnore，表示在序列化时忽略此字段
    private Set<Course> courses = new HashSet<>();

    // Getters and Setters
    public Long getId() { return id; }
    public void setId(Long id) { this.id = id; }
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }

    // 也可以将 @JsonIgnore 放在 getter 方法上
    // @JsonIgnore 
    public Set<Course> getCourses() { return courses; }
    public void setCourses(Set<Course> courses) { this.courses = courses; }
}

// Course.java (简化，仅为示例)
package com.example.demo.entity;

import jakarta.persistence.*;

@Entity
public class Course {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String title;

    // Getters and Setters
    public Long getId() { return id; }
    public void setId(Long id) { this.id = id; }
    public String getTitle() { return title; }
    public void setTitle(String title) { this.title = title; }
}