SpringBoot集成JPA

Posted 2020-10-22 小丸子的西瓜梦

JPA 注解的几个要点 

1.设置Pojo为实体 @Entity //标识这个pojo是一个jpa实体 public class Users implements Serializable{ } 

2.设置表名@Entity@table(name=users)//指表名为users public class Users implements Serializable{ } 

3.设置主键 public 

JPA 注解的几个要点 

@Entity

1.设置Pojo为实体 

public class Users implements Serializable {     
}    

2.设置表名 

@Entity     
@Table(name = "users") //指定表名为users     
public class Users implements Serializable {     
}    

3.设置主键 

public class Users implements Serializable {     
@Id     
private String userCode;  

4. 设置字段类型 

通过@Column注解设置，包含的设置如下 

name：字段名 
.unique：是否唯一 
.nullable：是否可以为空 
.inserttable：是否可以插入 
.updateable：是否可以更新 
.columnDefinition: 定义建表时创建此列的DDL 
.secondaryTable: 从表名。如果此列不建在主表上（默认建在主表），该属性定义该列所在从表的名字。 

1.创建新的maven项目

2. 添加必须的依赖

<?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.xlei</groupId>
    <artifactId>springboot_jpa</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>springboot_jpa</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.9.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-data-jpa</artifactId>
        </dependency>
        <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>

        <!--mysql驱动-->
        <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>

3. 新建springboot启动类

package com.xlei;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class SpringbootJpaApplication {

    public static void main(String[] args) {
        SpringApplication.run(SpringbootJpaApplication.class, args);
    }
}

4. 在resources跟目录下新建application.properties

#建立/更新数据表的配置
spring.jpa.hibernate.ddl-auto=update
#数据库地址
spring.datasource.url=jdbc:mysql://localhost:3306/user
#数据库名
spring.datasource.username=root
#数据库密码
spring.datasource.password=123456

• update:Hibernate根据给定的Entity结构改变数据库。
• create: 每次都会创建数据库,关闭时不会删除
• none: mysql的默认设置 , 不改变数据结构
• create-drop: 创建数据库,但是每次sessionFactory关闭后都会删除

5. 新建实体类User

这个时候其实已经可以启动springboot, 但是不会生成数据表,因为还没有配置实体类的jpa

package com.xlei.domain;

import javax.persistence.*;

/**
 * @Author:LeiXiao
 * @Description:SpringCloud
 * @Date:2018/1/30
 */
@Entity //标明这个需要生成数据表类型
@Table(name = "users")
public class User {

    @Id  // 声明一个策略通用生成器，name为”system-uuid”,策略strategy为”uuid”。
    @GeneratedValue
    private Integer id;
    @Column(nullable = false)
    private String name;
    @Column(nullable = false)
    private Integer age;
    @Column(nullable = false)
    private Boolean sex;

    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;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public Boolean getSex() {
        return sex;
    }

    public void setSex(Boolean sex) {
        this.sex = sex;
    }


}

这时候启动项目,就会在指定位置下生成一个user数据表

6. 实现CRUD

CrudRepository是一个提供了普通增删改查方法的接口,由spring内部提供,我们只需调用即可

新建UserRepository.java

public  interface UserRepository extends CrudRepository<User, String> {

}

7. 实现controller控制

新建UserController.java

package com.xlei.controller;

import com.xlei.dao.UserRepository;
import com.xlei.domain.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

/**
 * @Author:LeiXiao
 * @Description:SpringCloud
 * @Date:2018/1/30
 */
@RestController //将users纳入到spring容器中
public class UsersController {
    //自动装配
    @Autowired
    private UserRepository userRepository;
     @RequestMapping("/list")
    public Iterable<User> list(){
         Iterable<User> all = userRepository.findAll();
         return all;
     }
}