【发布时间】：2020-07-30 18:39:55
【问题描述】：
我是 Spring Boot 和 Spring Data JPA 的初学者。我正在尝试从表中获取所有数据，并且还想通过用户名获取数据，所以我在我的存储库中使用 findAll() 和 findByUsername(String username) 方法。我在我的存储库界面中扩展了 JpaRepository。但无法获取数据。 findAll() 返回空对象 findByUsername 返回空对象。表中有一条记录。还有一件事，repository.save(object) 方法工作正常。仅在 find 方法中面临问题。
我的存储库界面。
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;
import com.SpringBoot.model.User;
@Repository
public interface UserRepository extends JpaRepository<User, Long> {
User findByUsername(String username);
}
我的服务等级。
@Service
public class UserServiceImp {
UserRepository userRepository;
public List<User> getAllUsers() throws Exception {
return (List<User>) userRepository.findAll();
}
public User getUserById(String username) throws Exception {
System.out.println("in service imp class ***************************");
return userRepository.findByUsername(username);
}
public void addUsers(User user) throws Exception {
userRepository.save(user);
}
}
我的实体类。
@Entity
public class User implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
private String username;
private String name;
private int userCode;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getUserCode() {
return userCode;
}
public void setUserCode(int userCode) {
this.userCode = userCode;
}
}
我的控制器
package com.SpringBoot.controller;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
import com.SpringBoot.model.User;
import com.SpringBoot.service.Userservice;
@RestController
public class UserController {
@Autowired
UserServiceImp userservice;
@PostMapping("/user/add")
public void addUsers(@RequestBody User user) {
try {
userservice.addUsers(user);
} catch (Exception e) {
e.printStackTrace();
}
}
@GetMapping("/user/{id}")
public User getUserById(@PathVariable("id") String username) {
User user = null;
try {
System.out.println("*************** " + username);
user = userservice.getUserById(username);
} catch (Exception e) {
e.printStackTrace();
}
return user;
}
@GetMapping(value = "/users")
public List<User> getAllUser() {
List<User> user = new ArrayList<User>();
System.out.println("*************** ");
try {
user = userservice.getAllUsers();
} catch (Exception e) {
e.printStackTrace();
}
return user;
}
}
我的 pom.xml
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.test.junit</groupId>
<artifactId>SpringBoot</artifactId>
<version>0.0.1-SNAPSHOT</version>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.2.1.RELEASE</version>
</parent>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.9.4</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
【问题讨论】：
-
当您在查询数据库时从未得到任何结果时，您怎么知道保存方法工作正常？另外：您的交易边界在哪里？
-
我已经使用 save() 在表中成功插入了一条记录。
标签： java spring-boot spring-data-jpa spring-data