JpaRepository 简单条件查询

      JpaRepository继承自PagingAndSortingRepository接口，JpaRepository基于JPA的Repository接口，极大减少了JPA作为数据访问的代码，JpaRepository是实现Spring Data JPA技术访问数据库的关键接口。

示例：简单条件查询

创建持久化类

程序清单：/jpa/src/main/java/com/dwx/bean/User.java

package com.dwx.bean;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;
@Entity
@Table(name="t_user")
public class User {
	@Id
	@GeneratedValue(strategy = GenerationType.IDENTITY)
	private Integer userId;
	private String userName;
	private String sex;
	private Integer age;
	public User() {}
	public User(String userName,String sex,Integer age) {
		this.userName=userName;
		this.sex=sex;
		this.age=age;
	}
	public Integer getUserId() {
		return userId;
	}
	public void setUserId(Integer userId) {
		this.userId = userId;
	}
	public String getUserName() {
		return userName;
	}
	public void setUserName(String userName) {
		this.userName = userName;
	}
	public String getSex() {
		return sex;
	}
	public void setSex(String sex) {
		this.sex = sex;
	}
	public Integer getAge() {
		return age;
	}
	public void setAge(Integer age) {
		this.age = age;
	}
}

定义数据访问层接口

程序清单：/jpa/src/main/java/com/dwx/repository/UserRepository.java

package com.dwx.repository;
import java.util.List;

import org.springframework.data.jpa.repository.JpaRepository;
import com.dwx.bean.User;
public interface UserRepository extends JpaRepository {
	User findByUserName(String userName);
	List findByUserNameAndAge(String userName,Integer age);
	List findByUserNameLike(String userName);
}

定义业务层类

程序清单：/jpa/src/main/java/com/dwx/service/UserService.java

package com.dwx.service;
import java.util.List;
import javax.annotation.Resource;
import javax.transaction.Transactional;
import org.springframework.stereotype.Service;
import com.dwx.bean.User;
import com.dwx.repository.UserRepository;
@Service
public class UserService {
	@Resource
	private UserRepository userRepository;
	
	@Transactional
	public void saveAll(List users) {
		userRepository.saveAll(users);
	}
	
	public User getUserByUserName(String userName) {
		return userRepository.findByUserName(userName);
	}
	
	public List getUserByUserNameAndAge(String userName,Integer age){
		return userRepository.findByUserNameAndAge(userName, age);
	}
	
	public List getUserByUserNameLike(String userName){
		return userRepository.findByUserNameLike(userName);
	}
}

定义控制器类

程序清单：/jpa/src/main/java/com/dwx/controller/UserController.java

package com.dwx.controller;
import java.util.ArrayList;
import java.util.List;
import javax.annotation.Resource;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import com.dwx.bean.User;
import com.dwx.service.UserService;
@RestController
@RequestMapping("/user")
public class UserController {
	@Resource
	private UserService userService;
	
	@RequestMapping("/save")
	public String save() {
		User user1=new User("john","男",25);
		User user2=new User("lucy","女",18);
		User user3=new User("Tom","男",16);
		List users=new ArrayList<>();
		users.add(user1);
		users.add(user2);
		users.add(user3);
		userService.saveAll(users);
		return "保存成功";
	}
	
	@RequestMapping("/userName")
	public User getByUserName(String userName){
		return userService.getUserByUserName(userName);
	}
	
	@RequestMapping("/userNameAndAge")
	public List getByUserNameAndAge(String userName,Integer age){
		return userService.getUserByUserNameAndAge(userName, age);
	}
	
	@RequestMapping("/userNameLike")
	public List getByUserNameLike(String userName){
		return userService.getUserByUserNameLike(userName);
	}
}

测试应用

添加用户信息，在浏览器中输入以下地址：http://localhost:8080/user/save

根据姓名和年龄查询，在浏览器中输入以下地址：http://localhost:8080/user/userNameAndAge?userName=john&age=25

根据姓名模糊查询，在浏览器中输入以下地址：http://localhost:8080/user/userNameLike?userName=jack