Spring JpaRepository findAll(example) 方法返回一个空列表

Question

I am working on an application in Spring and have run into an issue I can't find any info on.

I have a SpringMVC Get route that I expect to return a list of Users filtered based on the user's request params.

Here's the specific code:

    @GetMapping("/admin/users/filtered")
    public String adminUserPageFiltered(@RequestParam String role, Model model) {
        ExampleMatcher matcher = ExampleMatcher
                .matchingAll()
                .withIgnoreNullValues()
                .withMatcher("role", contains().ignoreCase());
        User example = new User();
        example.setRole(role);
        System.out.println("example role: " + example.getRole());
        Iterable<User> userList = userRepository.findAll(Example.of(example, matcher));
        System.out.println("Userlist: " + userList);
        model.addAttribute("users", userList);
        return "adminUserPage";

    }

As you can see here, the basic program flow is that a param is passed to this route, it creates a new User object with the values set by the param (currently only "Role" but I expect that to change over time)

The findAll method then looks for all records where role = the role param value;

In other words, my SQL query would look like this:

SELECT * FROM users WHERE role="myParam"

Running this query where role="admin" returns 1 record currently, which is expected.

But the findAll(example) in the java code above returns 0 records.

Can anyone tell me why the findAll method is not finding any records, and returning and empty list?

Here is some other code that may be relevant

User.java

public class User {

    @Id
    @Column(name = "user_id")
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    private String username;
    private String password;
    private String role;
    private boolean enabled;

    public void setUsername(String username) {
        this.username = username;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public void setRole(String role) {
        this.role = role;
    }

    public void setEnabled(boolean enabled) {
        this.enabled = enabled;
    }

    public String getPassword() {
        return password;
    }

    public String getUsername() {
        return username;
    }

    public String getRole() {
        return role;
    }

    public boolean getEnabled() {
        return enabled;
    }

    public Long getId() {
        return id;
    }

}

UserRepository.java

import com.example.sprintauthexample.model.User;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.query.Param;


public interface UserRepository extends JpaRepository<User, Long> {

    @Query("SELECT u FROM User u WHERE u.username = :username")
    public User getUserByUsername(@Param("username") String username);

    @Query("SELECT COUNT(u) FROM User u WHERE u.enabled = true")
    public int getUserCount();

    @Query("SELECT COUNT(role) FROM User u WHERE u.role='USER' AND u.enabled=true")
    public int getUserRoleCount();
}

EDIT Following advice from Jens Schrauder, I logged the generated query, which is below:

select user0_.user_id as user_id1_0_, user0_.enabled as enabled2_0_, user0_.password as password3_0_, user0_.role as role4_0_, user0_.username as username5_0_ from users user0_ where (lower(user0_.role) like ? escape ?) and user0_.enabled=?

with binding

2021-02-17 20:29:35.214 TRACE 14700 --- [nio-8080-exec-1] o.h.type.descriptor.sql.BasicBinder      : binding parameter [1] as [VARCHAR] - [%admin%]
2021-02-17 20:29:35.214 TRACE 14700 --- [nio-8080-exec-1] o.h.type.descriptor.sql.BasicBinder      : binding parameter [2] as [CHAR] - [\]
2021-02-17 20:29:35.215 TRACE 14700 --- [nio-8080-exec-1] o.h.type.descriptor.sql.BasicBinder      : binding parameter [3] as [BOOLEAN] - [false]

To be completely honest, I'm not completely sure what this means, exactly. I'm reading up on it currently, but if anyone knows, i'm certainly grateful if you share your knowledge or can point me in the right direction.

I'm happy to add more info as needed. Thanks to anyone who finds the answer!

Answer 1

I'm no Java expert but I've fixed the issue, here's how.

The "enabled" field is set to TRUE for every user in the db. The example was generated enabled to "false"

I believe the reason for this is that a NULL value in a boolean is false. That's how it would be in JavaScript, which is my main language. Java I'm still learning, but I'm happy with this explanation. Perhaps someone with more understanding and experience with Java can correct me.