java - Spring boot userRepository.findAll() 显示太多次并导致 stackoverflow 错误

Question

我有这段代码，但浏览器上的输出不是我想要的

@GetMapping(path = "/all")
public @ResponseBody List<User> getAllUsers() {
    return userRepository.findAll();
}

输出:

[{"id":4,"firstName":"busayo","lastName":"amowe","email":"amoweolubusayo@gmail.com","password":"$2a$10$09kGDhlEp.Xmj0ocDjGLTO.03z.kGQKm2ZHcsNetDpH0r6m1rkVIu","roles":[{"id":1,"name":"ROLE_ADMIN","users":[{"id":4,"firstName":"busayo","lastName":"amowe","email":"amoweolubusayo@gmail.com","password":"$2a$10$09kGDhlEp.Xmj0ocDjGLTO.03z.kGQKm2ZHcsNetDpH0r6m1rkVIu","roles":[{"id":1,"name":"ROLE_ADMIN","users":[{"id":4,"firstName":"busayo","lastName":"amowe","email":"amoweolubusayo@gmail.com","password":"$2a$10$09kGDhlEp.Xmj0ocDjGLTO.03z.kGQKm2ZHcsNetDpH0r6m1rkVIu","roles":[{"id":1,"name":"ROLE_ADMIN","users":[{"id":4,"firstName":"busayo","lastName":"amowe","email":"amoweolubusayo@gmail.com","password":"$2a$10$09kGDhlEp.Xmj0ocDjGLTO.03z.kGQKm2ZHcsNetDpH0r6m1rkVIu","roles":[{"id":1,"name":"ROLE_ADMIN","users":[{"id":4,"firstName":"busayo","lastName":"amowe","email":"amoweolubusayo@gmail.com","password":"$2a$10$09kGDhlEp.Xmj0ocDjGLTO.03z.kGQKm2ZHcsNetDpH0r6m1rkVIu","roles":[{"id":1,"name":"ROLE_ADMIN","users":[{"id":4,"firstName":"busayo","lastName":"amowe","email":"amoweolubusayo@gmail.com","password":"$2a$10$09kGDhlEp.Xmj0ocDjGLTO.03z.kGQKm2ZHcsNetDpH0r6m1rkVIu","roles":[{"id":1,"name":"ROLE_ADMIN","users":[{"id":4,"firstName":"busayo","lastName":"amowe","email":"amoweolubusayo@gmail.com","password":"$2a$10$09kGDhlEp.Xmj0ocDjGLTO.03z.kGQKm2ZHcsNetDpH0r6m1rkVIu","roles":[{"id":1,"name":"ROLE_ADMIN","users":[{"id":4,"firstName":"busayo","lastName":"amowe","email":"amoweolubusayo@gmail.com","password":"$2a$10$09kGDhlEp.Xmj0ocDjGLTO.03z.kGQKm2ZHcsNetDpH0r6m1rkVIu","roles":[{"id":1,"name":"ROLE_ADMIN","users":[{"id":4,"firstName":"busayo","lastName":"amowe","email":"amoweolubusayo@gmail.com","password":"$2a$10$09kGDhlEp.Xmj0ocDjGLTO.03z.kGQKm2ZHcsNetDpH0r6m1rkVIu","roles":[{"id":1,"name":"ROLE_ADMIN","users":[{"id":4,"firstName":"busayo","lastName":"amowe","email":"amoweolubusayo@gmail.com","password":"$2a$10$09kGDhlEp.Xmj0ocDjGLTO.03z.kGQKm2ZHcsNetDpH0r6m1rkVIu","roles":[{"id":1,"name":"ROLE_ADMIN","users":[{"id":4,"firstName":"busayo","lastName":"amowe","email":"amoweolubusayo@gmail.com","password":"$2a$10$09kGDhlEp.Xmj0ocDjGLTO.03z.kGQKm2ZHcsNetDpH0r6m1rkVIu","roles":[{"id":1,"name":"ROLE_ADMIN","users":[{"id":4,"firstName":"busayo","lastName":"amowe","email":"amoweolubusayo@gmail.com","password":"$2a$10$09kGDhlEp.Xmj0ocDjGLTO.03z.kGQKm2ZHcsNetDpH0r6m1rkVIu","roles":[{"id":1,"name":"ROLE_ADMIN","users":[{"id":4,"firstName":"busayo","lastName":"amowe","email":"amoweolubusayo@gmail.com","password":"$2a$10$09kGDhlEp.Xmj0ocDjGLTO.03z.kGQKm2ZHcsNetDpH0r6m1rkVIu","roles":[{"id":1,"name":"ROLE_ADMIN","users":[{"id":4,"firstName":"busayo","lastName":"amowe","email":"amoweolubusayo@gmail.com","password":"$2a$10$09kGDhlEp.Xmj0ocDjGLTO.03z.kGQKm2ZHcsNetDpH0r6m1rkVIu","roles":[{"id":1,"name":"ROLE_ADMIN","users"

不是应该打印一次吗？它显示 StackOverFlow 错误，而我的 getJson 函数无法显示它。我能做什么？

Answer 1

user 之间存在循环依赖关系和user role实体。

为了将您的回复返回给客户，您的 List<User>必须序列化。你必须告诉 Jackson 如何处理循环，否则它将因堆栈溢出异常而失败。

public class User {

    @JsonBackReference
    public List<Role> roles;

    // ...       

}

public class Role {

    @JsonManagedReference
    public List<User> users;

    // ...       

}

有关双向关系的 Jackson 教程，请参阅 https://www.baeldung.com/jackson-bidirectional-relationships-and-infinite-recursion