orm-04-Spring Data JPA 入门介绍

老马啸西风2016年5月21日大约 4 分钟

拓展阅读

The jdbc pool for java.(java 手写 jdbc 数据库连接池实现)

The simple mybatis.（手写简易版 mybatis）

Spring Data JPA

Spring Data JPA，作为更大的 Spring Data 家族的一部分，使得基于 JPA 的仓库实现变得更加容易。

该模块提供了对基于 JPA 的数据访问层的增强支持。

它使得构建使用数据访问技术的、由 Spring 驱动的应用程序变得更加容易。

Spring Data JPA 2.0.2.RELEASE

ps: spring data 太大了，就从 jpa 一个点入手。学习运用并了解其设计思想。

Hello World

spring-data-jpa（java-persist-api ）默认使用 Hibernate 作为实现。

完整代码地址

项目结构

├── spring-data-jpa
│   ├── pom.xml
│   ├── src
│   │   ├── main
│   │   │   ├── java
│   │   │   │   └── com
│   │   │   │       └── ryo
│   │   │   │           └── spring
│   │   │   │               └── data
│   │   │   │                   └── jpa
│   │   │   │                       ├── dao
│   │   │   │                       │   ├── EmployeeDAO.java
│   │   │   │                       │   └── EmployeeDAOImpl.java
│   │   │   │                       ├── model
│   │   │   │                       │   └── Employee.java
│   │   │   └── resources
│   │   │       ├── jdbc.properties
│   │   │       ├── spring
│   │   │       │   └── applicationContext-datasource.xml
│   │   │       └── sql
│   │   │           └── init.sql
│   │   └── test
│   │       └── java
│   │           └── SpringDataJPATest.java

属性及配置文件

pom.xml



    
        spring-data
        com.ryo
        1.0-SNAPSHOT
    
    4.0.0

    spring-data-jpa

    
        
            
                io.spring.platform
                platform-bom
                1.1.2.RELEASE
                pom
                import
            
        
    

    
        
            org.springframework.boot
            spring-boot-starter-data-jpa
        

        
            com.h2database
            h2
        
        
            mysql
            mysql-connector-java
        
        
            org.springframework
            spring-aop
        

        
            org.springframework
            spring-test
        

        
            junit
            junit

init.sql

测试时建立的数据库为 spring_data。

脚本用于新建表，内容如下：

CREATE TABLE `Employee` (
  `id` int(11) unsigned NOT NULL COMMENT '主键',
  `name` varchar(20) DEFAULT NULL COMMENT '名称',
  `role` varchar(20) DEFAULT NULL COMMENT '角色',
  PRIMARY KEY (`id`))
  ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT '雇员表';

jdbc.properties

jdbc.driverClassName=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://127.0.0.1:3306/spring_data?useUnicode=true&characterEncoding=UTF-8&useOldAlias
jdbc.username=root
jdbc.password=123456

applicationContext-datasource.xml

代码

EmployeeDAO.java

import com.ryo.spring.data.jpa.model.Employee;

import java.util.List;

public interface EmployeeDAO {
    //Create
    void save(Employee employee);
    //Read
    Employee getById(int id);
    //Update
    void update(Employee employee);
    //Delete
    void deleteById(int id);
    //Get All
    List getAll();
}

EmployeeDAOImpl.java

import com.ryo.spring.data.jpa.model.Employee;
import org.springframework.stereotype.Repository;

import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;
import javax.transaction.Transactional;
import java.util.List;

@Transactional
@Repository
public class EmployeeDAOImpl implements EmployeeDAO {
    @PersistenceContext
    EntityManager em;

    @Override
    public void save(Employee employee) {
        em.persist(employee);
    }

    @Override
    public Employee getById(int id) {
        return em.find(Employee.class, id);
    }

    public void update(Employee employee) {
        em.merge(employee);
    }

    @Override
    public void deleteById(int id) {
        em.remove(this.getById(id));
    }

    @Override
    public List getAll() {
        CriteriaBuilder builder = em.getCriteriaBuilder();
        final CriteriaQuery query = builder.createQuery(Employee.class);
        return this.em.createQuery(query).getResultList();
    }
}

Employee.java

import javax.persistence.Entity;
import javax.persistence.Id;

@Entity
public class Employee {

    @Id
    private int id;
    private String name;
    private String role;

    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 getRole() {
        return role;
    }

    public void setRole(String role) {
        this.role = role;
    }

    @Override
    public String toString() {
        return "{ID=" + id + ",Name=" + name + ",Role=" + role + "}";
    }
}

测试代码

SpringDataJPATest.java

import com.ryo.spring.data.jpa.dao.EmployeeDAO;
import com.ryo.spring.data.jpa.model.Employee;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

import javax.annotation.Resource;
import java.util.Random;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = "classpath:spring/applicationContext-datasource.xml")
public class SpringDataJPATest {

    @Resource
    private EmployeeDAO employeeDAO;

    @Test
    public void saveTest(){
        Employee emp = new Employee();
        int rand = new Random().nextInt(1000);
        emp.setId(rand);
        emp.setName("Ryo");
        emp.setRole("Java Developer");
        employeeDAO.save(emp);
    }
}

直接运行测试，数据库数据如下：

+-----+------+----------------+
| id  | name | role           |
+-----+------+----------------+
| 493 | Ryo  | Java Developer |
+-----+------+----------------+

jar 包依赖

上述项目的 jar 包依赖如下：

+- org.springframework.boot:spring-boot-starter-data-jpa:jar:1.2.3.RELEASE:compile
|  +- org.springframework.boot:spring-boot-starter:jar:1.2.3.RELEASE:compile
|  |  +- org.springframework.boot:spring-boot:jar:1.2.3.RELEASE:compile
|  |  +- org.springframework.boot:spring-boot-autoconfigure:jar:1.2.3.RELEASE:compile
|  |  +- org.springframework.boot:spring-boot-starter-logging:jar:1.2.3.RELEASE:compile
|  |  |  +- org.slf4j:jul-to-slf4j:jar:1.7.11:compile
|  |  |  +- org.slf4j:log4j-over-slf4j:jar:1.7.11:compile
|  |  |  \- ch.qos.logback:logback-classic:jar:1.1.3:compile
|  |  |     \- ch.qos.logback:logback-core:jar:1.1.3:compile
|  |  \- org.yaml:snakeyaml:jar:1.14:compile
|  +- org.springframework.boot:spring-boot-starter-aop:jar:1.2.3.RELEASE:compile
|  |  +- org.aspectj:aspectjrt:jar:1.8.5:compile
|  |  \- org.aspectj:aspectjweaver:jar:1.8.5:compile
|  +- org.springframework:spring-core:jar:4.1.6.RELEASE:compile
|  +- org.springframework.boot:spring-boot-starter-jdbc:jar:1.2.3.RELEASE:compile
|  |  +- org.springframework:spring-jdbc:jar:4.1.6.RELEASE:compile
|  |  +- org.apache.tomcat:tomcat-jdbc:jar:7.0.59:compile
|  |  |  \- org.apache.tomcat:tomcat-juli:jar:7.0.59:compile
|  |  \- org.springframework:spring-tx:jar:4.1.6.RELEASE:compile
|  +- org.hibernate:hibernate-entitymanager:jar:4.3.8.Final:compile
|  |  +- org.jboss.logging:jboss-logging:jar:3.1.3.GA:compile
|  |  +- org.jboss.logging:jboss-logging-annotations:jar:1.2.0.Beta1:compile
|  |  +- org.hibernate:hibernate-core:jar:4.3.8.Final:compile
|  |  |  +- antlr:antlr:jar:2.7.7:compile
|  |  |  \- org.jboss:jandex:jar:1.1.0.Final:compile
|  |  +- dom4j:dom4j:jar:1.6.1:compile
|  |  |  \- xml-apis:xml-apis:jar:1.0.b2:compile
|  |  +- org.hibernate.common:hibernate-commons-annotations:jar:4.0.5.Final:compile
|  |  +- org.hibernate.javax.persistence:hibernate-jpa-2.1-api:jar:1.0.0.Final:compile
|  |  \- org.javassist:javassist:jar:3.18.1-GA:compile
|  +- javax.transaction:javax.transaction-api:jar:1.2:compile
|  +- org.springframework:spring-orm:jar:4.1.6.RELEASE:compile
|  +- org.springframework.data:spring-data-jpa:jar:1.7.2.RELEASE:compile
|  |  +- org.springframework.data:spring-data-commons:jar:1.9.2.RELEASE:compile
|  |  +- org.springframework:spring-context:jar:4.1.6.RELEASE:compile
|  |  |  \- org.springframework:spring-expression:jar:4.1.6.RELEASE:compile
|  |  +- org.slf4j:slf4j-api:jar:1.7.11:compile
|  |  \- org.slf4j:jcl-over-slf4j:jar:1.7.11:compile
|  \- org.springframework:spring-aspects:jar:4.1.6.RELEASE:compile
+- com.h2database:h2:jar:1.4.185:compile
+- mysql:mysql-connector-java:jar:5.1.34:compile
+- org.springframework:spring-aop:jar:4.1.6.RELEASE:compile
|  +- aopalliance:aopalliance:jar:1.0:compile
|  \- org.springframework:spring-beans:jar:4.1.6.RELEASE:compile
+- org.springframework:spring-test:jar:4.1.6.RELEASE:compile
\- junit:junit:jar:4.11:compile
   \- org.hamcrest:hamcrest-core:jar:1.3:compile

学习感想

说实在的，觉得 spring-data 设计的很棒。但是 mybatis 的使用门槛实在太低。所有以后可能还是专注于使用 mybatis。

贡献者

binbin.hou