初衷

項目中有用到spring data jpa，簡單看了一下，在基礎的數據庫操作上，要比mybatis好用，簡化了持久層的操作，使coder可以專注於業務邏輯的實現。網上參考了一些文章，實際coding的時候還是出好多錯誤。這裏通過CRUD，記錄摸索填坑的過程。詳細的概念可以參考文末的文章。

創建工程

創建一個maven工程。

配置

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

  <display-name>spring-jpa-web</display-name>
  <!-- spring mvc -->
  <servlet>
    <servlet-name>appServlet</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <init-param>
      <param-name>contextConfigLocation</param-name>
      <param-value>classpath:spring.xml</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
  </servlet>

  <servlet-mapping>
    <servlet-name>appServlet</servlet-name>
    <url-pattern>/</url-pattern>
  </servlet-mapping>

</web-app>

pom.xml

特別說明，spring-data-jpa要用版本1.9.0.RELEASE。

<?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/maven-v4_0_0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <groupId>org.wxs.spring</groupId>
    <artifactId>spring-jpa-web</artifactId>
    <packaging>war</packaging>
    <version>0.1.0</version>

    <properties>
        <spring_version>4.3.0.RELEASE</spring_version>
        <spring_jpa_version>1.9.0.RELEASE</spring_jpa_version>
        <spring_data_commons_version>1.12.6.RELEASE</spring_data_commons_version>
        <hibernate.version>4.2.5.Final</hibernate.version>
    </properties>

    <dependencies>

        <!-- PERSISTENCE begin -->
        <!--spring data jpa start-->
        <dependency>
            <groupId>org.springframework.data</groupId>
            <artifactId>spring-data-jpa</artifactId>
            <version>${spring_jpa_version}</version>
        </dependency>

        <!-- hibernate -->
        <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>org.hibernate</groupId>
            <artifactId>hibernate-ehcache</artifactId>
            <version>${hibernate.version}</version>
        </dependency>

        <!--連接池-->
        <dependency>
            <groupId>org.apache.tomcat</groupId>
            <artifactId>tomcat-jdbc</artifactId>
            <version>7.0.54</version>
        </dependency>

        <!--mysql-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.35</version>
        </dependency>

        <!-- spring start -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-core</artifactId>
            <version>${spring_version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-beans</artifactId>
            <version>${spring_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>org.springframework</groupId>
            <artifactId>spring-context</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>${spring_version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>${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-test</artifactId>
            <version>${spring_version}</version>
        </dependency>
        <!-- spring end -->
        <!-- test -->
        <dependency>
            <!--使用junit4-->
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <!--3.0是使用編程的方式-->
            <!--<version>3.8.1</version>-->
            <!--4.0使用註解的方式-->
            <!--SpringJUnit4ClassRunner requires JUnit 4.12 or higher-->
            <version>4.12</version>
            <scope>test</scope>
        </dependency>

        <!-- servlet start -->
        <dependency>
            <groupId>org.apache.tomcat</groupId>
            <artifactId>tomcat-servlet-api</artifactId>
            <version>8.0.3</version>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>org.apache.tomcat</groupId>
            <artifactId>jsp-api</artifactId>
            <version>6.0.39</version>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>jstl</groupId>
            <artifactId>jstl</artifactId>
            <version>1.2</version>
        </dependency>

        <dependency>
            <groupId>javax.servlet.jsp</groupId>
            <artifactId>jsp-api</artifactId>
            <version>2.1</version>
            <scope>provided</scope>
        </dependency>
        <!-- servlet end -->
    </dependencies>


</project>

spring.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:tx="http://www.springframework.org/schema/tx"
       xmlns:jpa="http://www.springframework.org/schema/data/jpa"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd
        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsd
        http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa-1.3.xsd"
       default-lazy-init="true">

    <description>Spring公共配置</description>

    <!--service包-->
    <context:component-scan base-package="com.wx.jpa"/>

    <!-- Jpa Entity Manager 配置 -->
    <bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
        <property name="dataSource" ref="dataSource"/>
        <property name="jpaVendorAdapter" ref="hibernateJpaVendorAdapter"/>
        <property name="packagesToScan" value="com.wx.jpa.entities"/>
        <property name="jpaProperties">
            <props>
                <!-- 命名規則 My_NAME->MyName -->
                <prop key="hibernate.ejb.naming_strategy">org.hibernate.cfg.ImprovedNamingStrategy</prop>
            </props>
        </property>

        <property name="jpaDialect">
            <bean class="org.springframework.orm.jpa.vendor.HibernateJpaDialect"/>
        </property>
    </bean>

    <bean id="hibernateJpaVendorAdapter" class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
        <property name="generateDdl" value="true"/>
        <property name="database" value="MYSQL"/>
        <property name="databasePlatform" value="org.hibernate.dialect.MySQLInnoDBDialect"/>
    </bean>

    <!-- Spring Data Jpa配置 -->
    <jpa:repositories base-package="com.wx.jpa.repository" transaction-manager-ref="transactionManager"
                      entity-manager-factory-ref="entityManagerFactory"/>

    <!-- Jpa 事務配置 -->
    <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
        <property name="entityManagerFactory" ref="entityManagerFactory"/>
    </bean>

    <!-- 使用annotation定義事務 -->
    <tx:annotation-driven transaction-manager="transactionManager" proxy-target-class="true"/>

    <bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
        <property name="dataSource" ref="dataSource"/>
    </bean>

    <!-- 數據源配置, 使用Tomcat JDBC連接池 -->
    <bean id="dataSource" class="org.apache.tomcat.jdbc.pool.DataSource" destroy-method="close">
        <!-- Connection Info -->
        <property name="driverClassName" value="${jdbc.driver}"/>
        <property name="url" value="${jdbc.url}"/>
        <property name="username" value="${jdbc.username}"/>
        <property name="password" value="${jdbc.password}"/>

        <!-- Connection Pooling Info -->
        <property name="maxActive" value="${jdbc.pool.maxActive}"/>
        <property name="maxIdle" value="${jdbc.pool.maxIdle}"/>
        <property name="minIdle" value="0"/>
        <property name="defaultAutoCommit" value="true"/>
    </bean>

    <!--數據庫連接-->
    <context:property-placeholder location="classpath:jdbc.properties"/>
</beans>

屬性文件

jdbc.properties

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/seckill?useUnicode=true&characterEncoding=utf8
jdbc.username=root
jdbc.password=admin
jdbc.pool.maxIdle=5
jdbc.pool.maxActive=10

Entity

新建表

新建表 user

實體類

新建實體類User

@Entity
@Table(name = "user")
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer  id;
    @Column(name = "name")
    private String name;
    @Column(name = "password")
    private String password;
    @Column(name = "birthday")
    private Date birthday;

    /**
     * The default constructor only exists for the sake of JPA. You won’t use it directly, so it is designated as protected.
     */
    protected User() {
    }

    public User(String name, String password, Date birthday) {
        this.name = name;
        this.password = password;
        this.birthday = birthday;
    }
getter、setter省略

DAO層

創建接口UserRepository

public interface UserRepository extends JpaRepository<User,Integer> {

}

測試

新增

    @Test
    public void test1(){
        User user=new User("SL1","123",new Date());
        userRepository.save(user);
        System.out.println("save success");
    }

查詢

查詢全部

    @Test
    public void test2(){
        for (User user:userRepository.findAll()) {
            System.out.println(user);
        }
        System.out.println("search all success");
    }

查詢結果

User{id=9, name='SL1', password='123', birthday=2017-01-12 00:00:00.0}
User{id=10, name='SL1', password='123', birthday=2017-01-12 00:00:00.0}
User{id=11, name='SL1', password='123', birthday=2017-01-13 00:00:00.0}
search all success

根據ID查詢

    @Test
    public void test3(){
        System.out.println(userRepository.findOne(9));
        System.out.println("search one success");
    }

查詢結果

User{id=9, name='SL1', password='123', birthday=2017-01-12 00:00:00.0}
search one success

更新

如果有Id，jpa會認爲是更新，沒有則是新增。

    @Test
    public void test4(){
        User user=new User("SL99","123",new Date());
        user.setId(9);
        userRepository.save(user);
        test3();
        System.out.println("update success");
    }

更新成功

User{id=9, name='SL99', password='123', birthday=2017-01-13 00:00:00.0}
search one success
update success

刪除

    @Test
    public void test5(){
        userRepository.delete(9);
        test3();
        System.out.println("delete success");
    }

刪除成功

null
search one success
delete success

踩過的坑

坑1

java.lang.AbstractMethodError: org.springframework.data.repository.core.support.RepositoryFactorySupport.getTargetRepository(Lorg/springframework/data/repository/core/RepositoryInformation;)Ljava/lang/Object;

解決方案

Deleting the spring-data-commons and changing the spring-data-jpa version to 1.9.0.RELEASE like @peeskillet said now works fine!
這也是爲什麼pom文件中spring-data-jpa要配置1.9.0.RELEASE的版本。

坑2

java.lang.IllegalArgumentException: Not an managed type: class java.lang.Object

解決方案

Dao層的接口繼承JpaRepository的時候加上泛型。添加域對象類型和主鍵類型。

public interface UserRepository extends JpaRepository<User,Integer>

坑3

org.hibernate.InstantiationException: No default constructor for entity: com.wx.jpa.entities.User

新增、根據ID查詢這2個方法不會報這個異常。

Hibernate在創建Bean的時候需要User的默認構造方法。Accessing Data with JPA中也有講到。
You also have two constructors. The default constructor only exists for the sake of JPA. You won’t use it directly, so it is designated as protected. The other constructor is the one you’ll use to create instances of Customer to be saved to the database.

歡迎感興趣的同學指正。。。

參考：
【原創】純乾貨，Spring-data-jpa詳解，全方位介紹。
瞭解 Spring Data JPA

spring data jpa 入門

初衷

創建工程

配置

web.xml

pom.xml

spring.xml

屬性文件

Entity

新建表

實體類

DAO層

測試

新增

查詢

查詢全部

根據ID查詢

更新

刪除

踩過的坑

坑1

解決方案

坑2

解決方案

坑3

解決方案

Java 覆蓋equals和hashCode方法

Servlet-過濾器入門

併發模式（二）Master-Worker模式

Servlet 過濾器詳解

spring data jpa 入門

Mac下配置sublime實現LaTeX

https://yachay.unat.edu.pe/blog/index.php?comment_area=format_blog&comment_component=blog&comment_co

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