SpringBoot使用spring data jpa

引言：

在相当长的一段时间内，实现应用程序的数据访问层一直很麻烦。必须编写太多样板代码来执行简单查询以及执行分页和审计。 Spring Data JPA旨在通过减少实际需要的工作量来显著改善数据访问层的实现。作为开发人员，您编写repository接口，包括自定义查找器方法，Spring将自动提供实现。

Spring Data JPA旨在通过减少实际需要的工作量来显著改善数据访问层的实现。作为开发人员，您编写repository接口，包括自定义查找器方法，Spring将自动提供实现。

代码编写：

1.依赖配置：

<?xml version="1.0" encoding="UTF-8"?>
<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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.wf</groupId>
    <artifactId>springbootdemo</artifactId>
    <version>1.0-SNAPSHOT</version>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.2.RELEASE</version>
    </parent>

    <!-- 添加spring mvc 依赖-->
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>

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

        <!--FreeMarker 模板引擎-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-freemarker</artifactId>
        </dependency>

        <!--整合springboot与mybatis的整合-->
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>1.1.1</version>
        </dependency>

        <!--测试junit-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

        <!--redis缓存-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-redis</artifactId>
        </dependency>

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

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

    </dependencies>
        <!--将mapper下的mapper接口与mapper映射文件放在一个mapper包下所需要的依赖-->
    <build>
        <resources>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>false</filtering> </resource> <resource> <directory>src/main/resources</directory> <includes> <include>**/*.*</include> </includes> <filtering>false</filtering> </resource> </resources> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build> </project>

2.resources配置application.properties：

#DB Configation
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.datasource.url=jdbc:mysql://localhost:3306/test
spring.datasource.username=root spring.datasource.password=root #JPA Configation spring.jpa.database=MySQL spring.jpa.generate-ddl=true spring.jpa.show-sql=true

如果连接不上数据库，那改成这段配置

#DB Configration
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.url=jdbc:mysql://localhost:3306/数据库名称?useUnicode=true&characterEncoding=utf-8&useSSL=false&serverTimezone = GMT
spring.datasource.username=root spring.datasource.password=root #JAPConfigration spring.jpa.database=MySQL spring.jpa.show-sql=true spring.jpa.generate-ddl=true

也可以使用19年初刚出的新技术spring data jpa（是爷爷辈，jpa是父辈，Hibernate是孙子辈--->已差不多被淘汰）

3.设置测试controller：

package com.wf.controller;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController; import java.util.HashMap; import java.util.Map; @RestController @RequestMapping("/test") public class TestController { @RequestMapping("/hello") public Map sayHell0(){ Map map=new HashMap(); map.put("json数据01","我爱java"); return map; } }

效果图：

进入正题：

1.创建数据库并添加数据：

2.创建对应的pojo对象：

package com.wf.entity;

import javax.persistence.*;

//标记此类为实体类 @Entity //标记对应的数据库中的表 @Table(name = "user") public class User { //设置id为主键 自增  @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Integer id; private String username; private String password; private String name; public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } public String getName() { return name; } public void setName(String name) { this.name = name; } @Override public String toString() { return "User{" + "id=" + id + ", username='" + username + '\'' + ", password='" + password + '\'' + ", name='" + name + '\'' + '}'; } public User(Integer id, String username, String password, String name) { this.id = id; this.username = username; this.password = password; this.name = name; } public User() { super(); } }

注意：对应的几个注解需要格外配置好

3.创建对应的controller接口：

package com.wf.controller;

import com.wf.dao.UserDao;
import com.wf.entity.User; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; import java.util.List; @RestController @RequestMapping("/user") public class UserController { @Autowired private UserDao userDao; //查询出所有数据 @RequestMapping("/list") public List<User> getUserList(){ return userDao.findAll(); } }

4.对应的dao层：

package com.wf.dao;


import com.xhn.entity.User;
import org.springframework.data.jpa.repository.JpaRepository; public interface UserDao extends JpaRepository<User,Integer> { }

代码测试：

本博主对应的json插件为：JSON-handle_0.5.6.crx，可以在网上自行百度

SpringBoot使用spring data jpa

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