JPA 註解的幾個要點

1.設置Pojo為實體 @Entity //標識這個pojo是一個jpa實體 public class Users implements Serializable{ }

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

3.設置主鍵 public

JPA 註解的幾個要點

@Entity

1.設置Pojo為實體

public class Users implements Serializable {
}

2.設置表名

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

3.設置主鍵

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

4. 設置字段類型

通過@Column註解設置，包含的設置如下

name：字段名
.unique：是否唯一
.nullable：是否可以為空
.inserttable：是否可以插入
.updateable：是否可以更新
.columnDefinition: 定義建表時創建此列的DDL
.secondaryTable: 從表名。如果此列不建在主表上（默認建在主表），該屬性定義該列所在從表的名字。

1.創建新的maven項目

2. 添加必須的依賴

<?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驅動-->
        <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啟動類

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跟目錄下新建application.properties

#建立/更新數據表的配置
spring.jpa.hibernate.ddl-auto=update
#數據庫地址
spring.datasource.url=jdbc:mysql://localhost:3306/user
#數據庫名
spring.datasource.username=root
#數據庫密碼
spring.datasource.password=123456

• update:Hibernate根據給定的Entity結構改變數據庫。
• create: 每次都會創建數據庫,關閉時不會刪除
• none: mysql的默認設置 , 不改變數據結構
• create-drop: 創建數據庫,但是每次sessionFactory關閉後都會刪除

5. 新建實體類User

這個時候其實已經可以啟動springboot, 但是不會生成數據表,因為還沒有配置實體類的jpa

package com.xlei.domain;

import javax.persistence.*;

/**
 * @Author:LeiXiao
 * @Description:SpringCloud
 * @Date:2018/1/30
 */
@Entity //標明這個需要生成數據表類型
@Table(name = "users")
public class User {

    @Id  // 聲明一個策略通用生成器，name為”system-uuid”,策略strategy為”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;
    }


}

這時候啟動項目,就會在指定位置下生成一個user數據表

6. 實現CRUD

CrudRepository是一個提供了普通增刪改查方法的接口,由spring內部提供,我們只需調用即可

新建UserRepository.java

public  interface UserRepository extends CrudRepository<User, String> {

}

7. 實現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 //將users納入到spring容器中
public class UsersController {
    //自動裝配
    @Autowired
    private UserRepository userRepository;
     @RequestMapping("/list")
    public Iterable<User> list(){
         Iterable<User> all = userRepository.findAll();
         return all;
     }
}

SpringBoot集成JPA