SpringDataJpa开发--继承JpaRepository实现简单条件查询

1.Spring Data JPA 是 Spring Data 技术下的子项目，使用Spring Data JPA 访问数据只需要数据访问层接口实现JpaRepository接口即可。

2.JpaRepository接口继承了PagingAndSortingRepository接口，所以也有它的一些功能

3.JpaRepoditory接口提供了很多常用方法：

示例：简单条件查询

按照Spring Data 的规则，我们可以通过定义在Repository接口下的方法来执行查询等操作

查询的方法必须以find、get、read开头，同时涉及条件查询时，Spring Data Jpa支持将条件属性定义在数据访问层接口下的方法名中

条件属性通过条件关键字连接。

条件属性的首字母必须大写

①创建一个Maven项目，在src/main下新建一个名为resources的文件夹，修改pom.xml

<groupId>com.ysh</groupId>
<artifactId>simplespringdatajpatest</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>

<name>simplespringdatajpatest</name>
<url>http://maven.apache.org</url>

<parent>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-parent</artifactId>
  <version>2.0.0.RELEASE</version>
  <relativePath/>
</parent>

   <properties>
  <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
  <java.version>1.8</java.version>
</properties>

<dependencies>


<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-web</artifactId>
</dependency>


<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>


    <dependency>
  <groupId>mysql</groupId>
  <artifactId>mysql-connector-java</artifactId>
</dependency>

         
     <dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>

    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <scope>test</scope>
    </dependency>
</dependencies>
</project>

②配置基本属性

在src/main/resources下新建一个全局配置文件，命名为application.properties

#数据库地址，其中springdatajpa是数据库名称

spring.datasource.url=jdbc:mysql://localhost:3306/springdatajpa

#数据库用户名

spring.datasource.username=root

#数据库密码，要改成自己的密码

spring.datasource.password=yourpassword

#数据库驱动，固定格式

spring.datasource.driverClassName=com.mysql.jdbc.Driver

#指定连接池中最大的活跃连接数

spring.datasource.max-active=20

#指定连接池最大的空闲连接

spring.datasource.max-idle=8

#指定必须保持连接的最小值

spring.datasource.min-idle=8

spring.datasource.initial-size=10

########################################################
### JPA持久化配置
########################################################
# 指定数据库类型
spring.jpa.database= MySQL
# 指定是否需要在日志中显示sql语句
spring.jpa.show-sql=true
# 指定自动创建|更新|验证数据库表结构等配置
# 表示如果数据库中存在持久化类对应的表就不创建，不存在就创建对应的表
spring.jpa.hibernate.ddl-auto= update
# 指定命名策略
spring.jpa.hibernate.naming-strategy=org.hibernate.cfg.ImprovedNamingStrategy
#指定数据库方言
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQL5Dialect

③创建持久化类

在com.ysh下新建4个包，bean(放置持久化类)、controller(控制器)、repository(定义数据访问接口的类)、service(业务逻辑处理类)

在bean下创建持久化类Student.java

package com.ysh.simplespringdatajpatest.bean;

import java.io.Serializable;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="tb_student")
public class Student implements Serializable{

private static final long serialVersionUID = 1L;

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;
private String name ;
private String address ;
private int age ;
private char sex;
public int getId() {
  return id;
}
public void setId(int id) {
  this.id = id;
}
public String getName() {
  return name;
}
public void setName(String name) {
  this.name = name;
}
public String getAddress() {
  return address;
}
public void setAddress(String address) {
  this.address = address;
}
public int getAge() {
  return age;
}
public void setAge(int age) {
  this.age = age;
}
public char getSex() {
  return sex;
}
public void setSex(char sex) {
  this.sex = sex;
}
}

④定义数据访问层接口

在repository包下新建一个接口，命名为StudentRepository,让该接口继承PagingAndSortingRepository

package com.ysh.simplespringdatajpatest.repository;

import java.util.List;

import org.springframework.data.jpa.repository.JpaRepository;

import com.ysh.simplespringdatajpatest.bean.Student;

public interface StudentRepository extends JpaRepository<Student, Integer> {

/**
* 通过学生姓名来查询学生对象
* 此方法相当于JPQL语句代码:select s from Student s where s.name = ?1
* @param name 参数
* @return Student对象
*/
Student findByName(String name);

/**
* 通过名字和地址查询学生信息
* 此方法相当于JPQL语句代码:select s from Student s where s.name = ?1 and s.address=?2
* @param name
* @param address
* @return 包含Student对象的List集合
*/
List<Student> findByNameAndAddress(String name , String address);

/**
* 通过学生姓名模糊查询学生信息
* 此方法相当于JPQL语句代码:select s from Student s where s.name like ?1
* @param name 参数
* @return 包含Student对象的List集合
*/
List<Student> findByNameLike(String name);

}

⑤定义业务层类

StudentService.java

package com.ysh.simplespringdatajpatest.service;

import java.util.List;

import javax.annotation.Resource;

import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import com.ysh.simplespringdatajpatest.bean.Student;
import com.ysh.simplespringdatajpatest.repository.StudentRepository;
@Service
public class StudentService {

// 注入数据访问层接口对象
@Resource
private StudentRepository studentRepository;

@Transactional
public void saveAll(List<Student> students) {
studentRepository.saveAll(students);
}

public Student getStuByName(String name) {
  return studentRepository.findByName(name);
}

public List<Student> getStusByNameAndAddress(String name,String address) {
  return studentRepository.findByNameAndAddress(name,address);
}

public List<Student> getStusByNameLike(String name) {
  return studentRepository.findByNameLike("%"+name+"%");
}
}

⑥定义控制器类

在controller包下新建控制器类，命名StudentController

package com.ysh.simplespringdatajpatest.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.ysh.simplespringdatajpatest.bean.Student;
import com.ysh.simplespringdatajpatest.service.StudentService;

@RestController
@RequestMapping("/student")
public class StudentController {

// 注入StudentService
@Resource
private StudentService studentService;

@RequestMapping("/save")
public String save() {
  Student swk = new Student();
  swk.setAddress("广州");
  swk.setName("孙悟空");
  swk.setAge(700);
  swk.setSex('男');

  Student zzj = new Student();
  zzj.setAddress("广州");
  zzj.setName("蜘蛛精");
  zzj.setAge(700);
  zzj.setSex('女');

  Student nmw = new Student();
  nmw.setAddress("广州");
  nmw.setName("牛魔王");
  nmw.setAge(500);
  nmw.setSex('男');

  List<Student> students = new ArrayList<>();
  students.add(swk);
  students.add(zzj);
  students.add(nmw);

  studentService.saveAll(students);
  return "保存学生对象成功";
}

@RequestMapping("/name")
public Student getByName(String name) {
  return studentService.getStuByName(name);
}

@RequestMapping("/nameAndAddress")
public List<Student> getByNameAndAddress(String name,String address) {
  return studentService.getStusByNameAndAddress(name, address);
}

@RequestMapping("/nameLike")
public List<Student> getByNameLile(String name) {
  return studentService.getStusByNameLike(name);
}

}

⑦测试应用

启动MySql数据库，新建数据库springdatajpa数据库

新建App.java启动类

package com.ysh.simplespringdatajpatest;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

/**
* @SpringBootApplication指定这是一个 spring boot的应用程序.
*/
@SpringBootApplication
public class App
{
    public static void main( String[] args )
    {
    // SpringApplication 用于从main方法启动Spring应用的类。
        SpringApplication.run(App.class, args);
    }
}

运行项目，JPA会在数据库中自动创建tb_student表

测试添加

浏览器中输入：http://localhost:8080/student/save

SpringDataJpa开发--继承JpaRepository实现简单条件查询