Spring data jpa + Hibernate

利用spring data及使用jpa規範，

大量簡化了dao接口的coding，

另外還可以使用spring data的許多介面幫忙實現實作，

也不需要撰寫一般常用的CRUD以及查詢實作，

只要撰寫介面後，spring data便會幫你完成實作的部分。


首先是maven的部分：

pom.xml

<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/maven-v4_0_0.xsd">
 <modelVersion>4.0.0</modelVersion>
 <groupId>com.springdata</groupId>
 <artifactId>springData</artifactId>
 <packaging>war</packaging>
 <version>0.0.1-SNAPSHOT</version>
 <name>springData Maven Webapp</name>
 <url>http://maven.apache.org</url>
 <properties>
  <spring.version>3.2.2.RELEASE</spring.version>
  <hibernate.version>4.2.0.Final</hibernate.version>
  <spring-data.version>1.3.0.RELEASE</spring-data.version>
 </properties>
 <dependencies>
  <dependency>
   <groupId>org.springframework</groupId>
   <artifactId>spring-beans</artifactId>
   <version>${spring.version}</version>
  </dependency>
  <dependency>
   <groupId>org.springframework</groupId>
   <artifactId>spring-core</artifactId>
   <version>${spring.version}</version>
  </dependency>
  <dependency>
   <groupId>org.springframework</groupId>
   <artifactId>spring-context-support</artifactId>
   <version>${spring.version}</version>
  </dependency>
  <dependency>
   <groupId>org.springframework</groupId>
   <artifactId>spring-context</artifactId>
   <version>${spring.version}</version>
  </dependency>
  <dependency>
   <groupId>org.springframework</groupId>
   <artifactId>spring-jdbc</artifactId>
   <version>${spring.version}</version>
  </dependency>
  <dependency>
   <groupId>org.springframework</groupId>
   <artifactId>spring-orm</artifactId>
   <version>${spring.version}</version>
  </dependency>
  <dependency>
   <groupId>org.springframework</groupId>
   <artifactId>spring-tx</artifactId>
   <version>${spring.version}</version>
  </dependency>
  <dependency>
   <groupId>org.springframework.data</groupId>
   <artifactId>spring-data-jpa</artifactId>
   <version>${spring-data.version}</version>
  </dependency>
  <dependency>
   <groupId>org.springframework</groupId>
   <artifactId>spring-web</artifactId>
   <version>${spring.version}</version>
  </dependency>
  <dependency>
   <groupId>org.springframework</groupId>
   <artifactId>spring-webmvc</artifactId>
   <version>${spring.version}</version>
  </dependency>
  <dependency>
   <groupId>mysql</groupId>
   <artifactId>mysql-connector-java</artifactId>
   <version>5.1.18</version>
  </dependency>
  <dependency>
   <groupId>junit</groupId>
   <artifactId>junit</artifactId>
   <version>3.8.1</version>
   <scope>test</scope>
  </dependency>
  <dependency>
   <groupId>org.hibernate</groupId>
   <artifactId>hibernate-core</artifactId>
   <version>${hibernate.version}</version>
  </dependency>
  <dependency>
   <groupId>org.hibernate</groupId>
   <artifactId>hibernate-entitymanager</artifactId>
   <version>${hibernate.version}</version>
  </dependency>
  <dependency>
   <groupId>commons-dbcp</groupId>
   <artifactId>commons-dbcp</artifactId>
   <version>1.4</version>
  </dependency>
 </dependencies>
 <build>
  <finalName>springData</finalName>
 </build>
</project>

接下來撰寫一個普通的POJO類，

User.java

package com.springdata.model;

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 = "USER")
public class User implements Serializable {
 /**
  * 
  */
 private static final long serialVersionUID = 1L;
 @Id
 @GeneratedValue(strategy = GenerationType.AUTO)
 private int id;
 private String name;

 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;
 }
}

其中需依照JPA規格制定table name，

以及id，GenerationType.AUTO設定為自動加號，

@column name沒設定的話直接預設為變數名稱，

接下來是最重要的dao，

UserRepository.java

package com.springdata.jpa;

import org.springframework.data.repository.CrudRepository;

import com.springdata.model.User;

public interface UserRepository extends JpaRepository<User, Integer> {

}

JpaRepository繼承CrudRepository、PagingAndSortingRepository等等的介面，

其中包含一些基本的save()、delete()、findAll()等等方法，

可以發現這裡沒有update()的方法，

其實save()裡面等同於hibernate的saveOrUpdate()。