一个泛型DAO例证

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

?

Sql代码?

1. create?table?TUser(??
2. ????id?char(32)?primary?key,??
3. ????name?char(20)??
4. )??

?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"?>

Xml代码?

1. <persistence?xmlns="http://java.sun.com/xml/ns/persistence"??
2. ????xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"??
3. ????xsi:schemaLocation="http://java.sun.com/xml/ns/persistence??
4. http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"??
5. ????version="2.0">??
6. ????<persistence-unit?name="demo"/>??
7. </persistence>??

?编写实体类并加上注解

?

Java代码?

1. package?com.tanlan.entity;??
2. ??
3. import?javax.persistence.Entity;??
4. import?javax.persistence.GeneratedValue;??
5. import?javax.persistence.Id;??
6. import?javax.persistence.Table;??
7. ??
8. import?org.hibernate.annotations.GenericGenerator;??
9. ??
10. @Entity??
11. @Table(name="TUser")??
12. public?class?User?{??
13. ????@Id??
14. ????@GenericGenerator(name="cuuid",strategy="uuid")??
15. ????@GeneratedValue(generator="cuuid")??
16. ????private?String?id;??
17. ????private?String?name;??
18. ??
19. ????public?String?getId()?{??
20. ????????return?id;??
21. ????}??
22. ??
23. ????public?void?setId(String?id)?{??
24. ????????this.id?=?id;??
25. ????}??
26. ??
27. ????public?String?getName()?{??
28. ????????return?name;??
29. ????}??
30. ??
31. ????public?void?setName(String?name)?{??
32. ????????this.name?=?name;??
33. ????}??
34. ??
35. }??

?定义父DAO

?该接口中定义共有方法，增删改查

?

Java代码?

1. package?com.tanlan.dao;??
2. ??
3. import?java.util.List;??
4. ??
5. public?interface?DAO<PK,E>?{??
6. ????void?persist(E?entity);??
7. ????void?remove(E?entity);??
8. ????E?findById(PK?id);??
9. ????List<E>?getAll();??
10. }??

?定义UserDAO接口

该接口声明了其他非公用方法

?package com.tanlan.dao;

Java代码?

1. import?com.tanlan.entity.User;??
2. ??
3. public?interface?UserDAO?extends?DAO<String,?User>?{??
4. ????void?otherMethod1();??
5. ????int?otherMethod2();??
6. }??

?实现公用方法

?

Java代码?

1. package?com.tanlan.dao;??
2. ??
3. import?java.lang.reflect.ParameterizedType;??
4. import?java.util.List;??
5. ??
6. import?org.springframework.orm.jpa.support.JpaDaoSupport;??
7. ??
8. ??
9. public?class?JpaDAO<PK,?E>?extends?JpaDaoSupport?implements?DAO<PK,?E>?{??
10. ????protected?Class<E>?entityClass;??
11. ??
12. ????@SuppressWarnings("unchecked")??
13. ????public?JpaDAO()?{??
14. ????????ParameterizedType?genericSuperclass?=?(ParameterizedType)?getClass()??
15. ????????????????.getGenericSuperclass();??
16. ????????this.entityClass?=?(Class<E>)?genericSuperclass??
17. ????????????????.getActualTypeArguments()[1];??
18. ????}??
19. ??
20. ????public?void?persist(E?entity)?{??
21. ????????getJpaTemplate().persist(entity);??
22. ????}??
23. ??
24. ????public?void?remove(E?entity)?{??
25. ????????getJpaTemplate().remove(entity);??
26. ????}??
27. ??
28. ????public?E?findById(PK?id)?{??
29. ????????return?getJpaTemplate().find(entityClass,?id);??
30. ????}??
31. ??
32. ????public?List<E>?getAll()?{??
33. ????????return?getJpaTemplate().find("from?"?+?entityClass.getName());??
34. ????}??
35. }??

?实现非公用方法的类

?

Java代码?

1. package?com.tanlan.dao;??
2. ??
3. import?com.tanlan.entity.User;??
4. ??
5. public?class?UserJpaDAO?extends?JpaDAO<String,?User>?implements?UserDAO?{??
6. ??
7. ????@Override??
8. ????public?void?otherMethod1()?{??
9. ????????//?TODO?Auto-generated?method?stub??
10. ????}??
11. ??
12. ????@Override??
13. ????public?int?otherMethod2()?{??
14. ????????//?TODO?Auto-generated?method?stub??
15. ????????return?0;??
16. ????}??
17. ??
18. }??

?编写Spring配置文件application.xml

?

Xml代码?

1. <?xml?version="1.0"?encoding="UTF-8"?>??
2. <beans?xmlns="http://www.springframework.org/schema/beans"??
3. ????xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"???
4. ????xmlns:aop="http://www.springframework.org/schema/aop"??
5. ????xmlns:tx="http://www.springframework.org/schema/tx"??
6. ????xsi:schemaLocation="http://www.springframework.org/schema/beans????
7. ???http://www.springframework.org/schema/beans/spring-beans-3.0.xsd??
8. ???http://www.springframework.org/schema/aop??
9. ???http://www.springframework.org/schema/aop/spring-aop-3.0.xsd??
10. ???http://www.springframework.org/schema/tx??
11. ???http://www.springframework.org/schema/tx/spring-tx-3.0.xsd">??
12. ????<bean?id="datasource"??
13. ????????class="org.springframework.jdbc.datasource.DriverManagerDataSource">??
14. ????????<property?name="driverClassName"?value="com.mysql.jdbc.Driver"?/>??
15. ????????<property?name="url"?value="jdbc:mysql://localhost/test"?/>??
16. ????????<property?name="username"?value="root"?/>??
17. ????????<property?name="password"?value="tanlan"></property>??
18. ????</bean>??
19. ????<bean?id="entityManageFactrory"??
20. ????????class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">??
21. ????????<property?name="dataSource"?ref="datasource"?/>??
22. ????????<property?name="jpaVendorAdapter">??
23. ????????????<bean?class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">??
24. ????????????????<property?name="database"?value="MYSQL"?/>??
25. ????????????????<property?name="generateDdl"?value="false"?/>??
26. ????????????????<property?name="showSql"?value="true"?/>??
27. ????????????</bean>??
28. ????????</property>??
29. ????</bean>??
30. ????<bean?id="transactionManager"?class="org.springframework.orm.jpa.JpaTransactionManager">??
31. ????????<property?name="entityManagerFactory"?ref="entityManageFactrory"?/>??
32. ????</bean>??
33. ??
34. ????<bean?id="userDAO"?class="com.tanlan.dao.UserJpaDAO">??
35. ????????<property?name="entityManagerFactory"?ref="entityManageFactrory"?/>??
36. ????</bean>??
37. ??????
38. ????<tx:advice?id="txAdvice"?transaction-manager="transactionManager">??
39. ????????<tx:attributes>??
40. ????????????<tx:method?name="get*"?propagation="SUPPORTS"?read-only="true"??/>??
41. ????????????<tx:method?name="*"?propagation="REQUIRED"?/>??
42. ????????</tx:attributes>??
43. ????</tx:advice>??
44. ?????<aop:config>??
45. ????????????<aop:advisor?advice-ref="txAdvice"??
46. ????????????????pointcut="execution(*?*..DAO.*(..))"?/>??
47. ????????</aop:config>??
48. </beans>??

?测试代码如下：

?

Java代码?

1. package?com.tanlan.test;??
2. ??
3. import?java.util.List;??
4. ??
5. import?org.springframework.context.ApplicationContext;??
6. import?org.springframework.context.support.ClassPathXmlApplicationContext;??
7. ??
8. import?com.tanlan.dao.UserDAO;??
9. import?com.tanlan.entity.User;??
10. ??
11. public?class?Test?{??
12. ??
13. ????public?static?void?main(String[]?args)?{??
14. ????????User?newUser=new?User();??
15. ????????newUser.setName("tanlan");??
16. ??????????
17. ????????ApplicationContext?context=new?ClassPathXmlApplicationContext("application.xml");??
18. ????????UserDAO?userDAO=context.getBean("userDAO",UserDAO.class);??
19. ????????userDAO.persist(newUser);??
20. ????????List<User>?users=userDAO.getAll();??
21. ????????for?(User?user?:?users)?{??
22. ????????????System.out.println(user.getName());??
23. ????????}??
24. ??
25. ????}??
26. ??
27. }??

?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：

?

?

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