一个泛型DAO例子

自从Java支持泛型后，使用ORM框架编写DAO的时候就可以结合泛型写出更简洁的代码。

    下面的小例子展示了使用Spring与JPA集成的环境下DAO的编写方法。

    开发测试环境：jdk1.6,Spring3.0.5,Hibernate3.6.2,MySQL5.5,MyEclispe9.0

数据库表结构

 

create table TUser(
    id char(32) primary key,
    name char(20)
)

 创建一个纯Java工程

  需要引入相应的jar文件，

 在src的META-INF下编写persistence.xml

 <?xml version="1.0" encoding="UTF-8"?>

<persistence xmlns="http://java.sun.com/xml/ns/persistence"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"
    version="2.0">
    <persistence-unit name="demo"/>
</persistence>

 编写实体类并加上注解

 

package com.tanlan.entity;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;

import org.hibernate.annotations.GenericGenerator;

@Entity
@Table(name="TUser")
public class User {
    @Id
    @GenericGenerator(name="cuuid",strategy="uuid")
    @GeneratedValue(generator="cuuid")
    private String id;
    private String name;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

}

 定义父DAO

 该接口中定义共有方法，增删改查

 

package com.tanlan.dao;

import java.util.List;

public interface DAO<PK,E> {
    void persist(E entity);
    void remove(E entity);
    E findById(PK id);
    List<E> getAll();
}

 定义UserDAO接口

该接口声明了其他非公用方法

 package com.tanlan.dao;

import com.tanlan.entity.User;

public interface UserDAO extends DAO<String, User> {
    void otherMethod1();
    int otherMethod2();
}

 实现公用方法

 

package com.tanlan.dao;

import java.lang.reflect.ParameterizedType;
import java.util.List;

import org.springframework.orm.jpa.support.JpaDaoSupport;


public class JpaDAO<PK, E> extends JpaDaoSupport implements DAO<PK, E> {
    protected Class<E> entityClass;

    @SuppressWarnings("unchecked")
    public JpaDAO() {
        ParameterizedType genericSuperclass = (ParameterizedType) getClass()
                .getGenericSuperclass();
        this.entityClass = (Class<E>) genericSuperclass
                .getActualTypeArguments()[1];
    }

    public void persist(E entity) {
        getJpaTemplate().persist(entity);
    }

    public void remove(E entity) {
        getJpaTemplate().remove(entity);
    }

    public E findById(PK id) {
        return getJpaTemplate().find(entityClass, id);
    }

    public List<E> getAll() {
        return getJpaTemplate().find("from " + entityClass.getName());
    }
}

 实现非公用方法的类

 

package com.tanlan.dao;

import com.tanlan.entity.User;

public class UserJpaDAO extends JpaDAO<String, User> implements UserDAO {

    @Override
    public void otherMethod1() {
        // TODO Auto-generated method stub
    }

    @Override
    public int otherMethod2() {
        // TODO Auto-generated method stub
        return 0;
    }

}

 编写Spring配置文件application.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:aop="http://www.springframework.org/schema/aop"
    xmlns:tx="http://www.springframework.org/schema/tx"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
   http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
   http://www.springframework.org/schema/aop
   http://www.springframework.org/schema/aop/spring-aop-3.0.xsd
   http://www.springframework.org/schema/tx
   http://www.springframework.org/schema/tx/spring-tx-3.0.xsd">
    <bean id="datasource"
        class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <property name="driverClassName" value="com.mysql.jdbc.Driver" />
        <property name="url" value="jdbc:mysql://localhost/test" />
        <property name="username" value="root" />
        <property name="password" value="tanlan"></property>
    </bean>
    <bean id="entityManageFactrory"
        class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
        <property name="dataSource" ref="datasource" />
        <property name="jpaVendorAdapter">
            <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
                <property name="database" value="MYSQL" />
                <property name="generateDdl" value="false" />
                <property name="showSql" value="true" />
            </bean>
        </property>
    </bean>
    <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
        <property name="entityManagerFactory" ref="entityManageFactrory" />
    </bean>

    <bean id="userDAO" class="com.tanlan.dao.UserJpaDAO">
        <property name="entityManagerFactory" ref="entityManageFactrory" />
    </bean>

    <tx:advice id="txAdvice" transaction-manager="transactionManager">
        <tx:attributes>
            <tx:method name="get*" propagation="SUPPORTS" read-only="true"  />
            <tx:method name="*" propagation="REQUIRED" />
        </tx:attributes>
    </tx:advice>
     <aop:config>
            <aop:advisor advice-ref="txAdvice"
                pointcut="execution(* *..DAO.*(..))" />
        </aop:config>
</beans>

 测试代码如下：

 

package com.tanlan.test;

import java.util.List;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.tanlan.dao.UserDAO;
import com.tanlan.entity.User;

public class Test {

    public static void main(String[] args) {
        User newUser=new User();
        newUser.setName("tanlan");

        ApplicationContext context=new ClassPathXmlApplicationContext("application.xml");
        UserDAO userDAO=context.getBean("userDAO",UserDAO.class);
        userDAO.persist(newUser);
        List<User> users=userDAO.getAll();
        for (User user : users) {
            System.out.println(user.getName());
        }

    }

}

 今后若要增加对其他表的DAO编写，只需按照此方法增加一个接口与一个类即可，公用的增删改查无需操心。

完整 的jar包列表如下：