无法在 Spring Boot 中使用 findOne() 方法

Question

My project is about a User-Manager web.

I'm a new in Spring and Java.

Here is my code:In the UserController

@RequestMapping(value="/users/{name}",method = RequestMethod.GET)
public User showUser(@PathVariable("name") String name){
    return userService.findUser(name);
}

In the UserService:

 public User findUser(String name){
    return userRepository.findOne(name);
}

And in the Postman when I go to the link: http://localhost:8080/users/hunghip4 (hunghip4 is a user I created)

{
  "timestamp": 1460570912129,
  "status": 500,
  "error": "Internal Server Error",
  "exception": "org.springframework.dao.InvalidDataAccessApiUsageException",
  "message": "Provided id of the wrong type for class     com.uet.dhqg.usermanage.model.User. Expected: class java.lang.Integer, got class java.lang.String; nested exception is java.lang.IllegalArgumentException: Provided id of the wrong type for class com.uet.dhqg.usermanage.model.User. Expected: class java.lang.Integer, got class java.lang.String",
  "path": "/users/hunghip4"
}

The User model:

@Entity
@Table(name="user")
public class User extends HypermediaLinks {
@Id
@Column(name="id")
private int id;
@Column(name="name")
private String name;
@Column(name="pass")
private String pass;

public int getId(){
    return id;
}

public String getName(){
    return name;
}

public void serName(String name){
    this.name = name;
}

public String getPass(){
    return pass;
}

public void serPass(String pass){
    this.pass = pass;
}

}

The UserRepository:

@Repository
public interface UserRepository extends CrudRepository<User,String>{
}

Answer 1

Your UserRepository is defined as CrudRepository<User,String> . Where User is the type and String the type of the id. However your User class has an id field of the type int NOT of type String .

First fix your UserRepository to be a proper representation of your User .

public interface UserRepository extends CrudRepository<User, Integer> {}

Next create a method to find your User by name.

public User findByName(String name);

And call this from your controller instead of findOne . The findOne is used to find entities based on ID not on any random field of your entity.

Answer 2

As the exception suggests, you are passing the user name to the findOne method. But as per the method signature in the Spring docs, the method findOne expects the ID which is an Integer as its argument. Pass the user ID instead of name.

Answer 3

Change your repository definition to

public interface UserRepository extends CrudRepository<User,Integer>

Your User id data type is int, so your repository Id should be int too. with this replacement findOne method also accepts integer data type as User id is.

Answer 4

Change the version of the above artifact to 1.4.0.RELEASE in pom file and do maven update project.

 <parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.4.0.RELEASE</version>
 </parent>

Answer 5

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.4.0.RELEASE</version>
    <relativePath/> <!-- lookup parent from repository -->
</parent>

Update Pom.xml and import maven changes

Answer 6

//Create a BookMarkRepsoitory extending the JpaRepo
```import org.springframework.data.jpa.repository.JpaRepository;
public interface BookMarkRepository
        extends JpaRepository<Book, String> {
}
```

then in your class to access one book or any value use this method
```
 @Override
                    public UserDetails loadBookBookname(String bookName)
                            throws UsernameNotFoundException {
                        Optional<Book> book= readerRepository.findById(bookName);
                        if (book.isPresent()){
                            return book.get();
                        }
                        else return null;
                    }```

Answer 7

<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.4.0.RELEASE</version>

It is helpful