SpringBoot + JPA整合

新建项目，在https://start.spring.io/ 中创建一个SprongBoot的项目，然后把它导入到你的开发工具中，如下图所示：

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项目的整体布局如下所示：

image.png

项目的pom.xml文件如下所示：

<?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>ni.ma</groupId>
    <artifactId>yang</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>yang</name>
    <description>project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.3.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </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.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <scope>compile</scope>
        </dependency>
        
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>
        
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>


</project>

配置application.properties文件，在该文件中添加配置数据的信息，如下所示：

spring.jpa.show-sql = true
logging.level.org.springframework.data=DEBUG
spring.jpa.hibernate.ddl-auto=

spring.datasource.url=jdbc\:mysql\://10.**.***.**\:3306/yangnima?useSSL=false
spring.datasource.username=root
spring.datasource.password=*******
spring.datasource.tomcat.max-active=100
spring.datasource.tomcat.max-idle=200
spring.datasource.tomcat.initialSize=20
spring.datasource.driver-class-name=com.mysql.jdbc.Driver

创建一个实体类TbText.java，代码如下：

package ni.ma.yang.entity;

import java.io.Serializable;

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

@Entity
@Table(name = "tb_text")
public class TbText implements Serializable{

    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    
    @Id
    @Column(name = "ID", nullable = false, updatable = false,length=11)
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Integer id;//自增长ID
    
    @Column(name = "name", nullable = true,length=15)
    private String name;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

实现一个持久层服务，那么我只需要声明一个接口，这个接口继承Repository 接口就可以了。自己实现一个通过id查询得到实体，代码如下所示：

package ni.ma.yang.repository;

import org.springframework.data.jpa.repository.JpaRepository;
import ni.ma.yang.entity.TbText;

public interface TbTextRepository extends JpaRepository<TbText, Long> {
    TbText findTbTextById(int id);

}

接下来就是验证了，创建一个TextController类，具体代码如下所示：

package ni.ma.yang.controller;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
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 ni.ma.yang.entity.TbText;
import ni.ma.yang.repository.TbTextRepository;

@RestController
@RequestMapping("/text")
public class TextController {
    private static final Logger LOGGER = LoggerFactory.getLogger(TextController.class);
    
    @Autowired
    private TbTextRepository tbTextRepository;
    
    @GetMapping("/findById")
    public void findById(int id) {
        TbText tb = tbTextRepository.findTbTextById(id);
        LOGGER.info("*****************" + tb.getName() + "*****************");
    }
}

在网页中输入：http://localhost:8080/text/findById?id=2 控制台输出如下所示：

*****************wanguniang*****************

去数据库中验证，当id是2时，name是wanguniang，正确。

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