JdbcTemplate详解 (2010-08-24 10:07:01)（转载）

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1、JdbcTemplate操作数据库Spring对数据库的操作在jdbc上面做了深层次的封装，使用spring的注入功能，可以把DataSource注册到JdbcTemplate之中。同时，为了支持对properties文件的支持，spring提供了类似于EL表达式的方式，把dataSource.properties的文件参数引入到参数配置之中，<context:property-placeholder location="classpath:jdbc.properties" />。
实例代码如下：提供数据源的相关配置信息：jdbc.propertiesdriverClassName=org.gjt.mm.mysql.Driver
url=jdbc\:mysql\://localhost\:3306/stanley?useUnicode\=true&characterEncoding\=UTF-8
username=root
password=123456
initialSize=1
maxActive=500
maxIdle=2
minIdle=1

提供spring的配置文件，将jdbc.properties与JdbcTemplate粘合起来的配置文件：beans.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: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-2.5.xsd
?????????????????????http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-2.5.xsd
?????????????????????http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.5.xsd
?????????????????????http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.5.xsd">

????<context:property-placeholder?location="classpath:jdbc.properties"/>
????<bean?id="dataSource"?class="org.apache.commons.dbcp.BasicDataSource"?destroy-method="close">
?????????<property?name="driverClassName"?value="${driverClassName}"/>
?????????<property?name="url"?value="${url}"/>
?????????<property?name="username"?value="${username}"/>
?????????<property?name="password"?value="${password}"/>
????????????<!--?连接池启动时的初始值?-->
?????<property?name="initialSize"?value="${initialSize}"/>
?????<!--?连接池的最大值?-->
?????<property?name="maxActive"?value="${maxActive}"/>
?????<!--?最大空闲值.当经过一个高峰时间后，连接池可以慢慢将已经用不到的连接慢慢释放一部分，一直减少到maxIdle为止?-->
?????<property?name="maxIdle"?value="${maxIdle}"/>
?????<!--????最小空闲值.当空闲的连接数少于阀值时，连接池就会预申请去一些连接，以免洪峰来时来不及申请?-->
?????<property?name="minIdle"?value="${minIdle}"/>
????</bean>

??<bean?id="txManager"?class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
????????????<property?name="dataSource"?ref="dataSource"/>
????????</bean>

??<aop:config>
????????<aop:pointcut?id="transactionPointcut"?expression="execution(* cn.comp.service..*.*(..))"/>
????????<aop:advisor?advice-ref="txAdvice"?pointcut-ref="transactionPointcut"/>
??</aop:config>
??<tx:advice?id="txAdvice"?transaction-manager="txManager">
????????<tx:attributes>
????????????<tx:method?name="get*"?read-only="true"?propagation="NOT_SUPPORTED"/>
????????????<tx:method?name="*"/>
????????</tx:attributes>
??</tx:advice>

??<bean?id="personService"?class="cn.comp.service.impl.PersonServiceBean">
????<property?name="dataSource"?ref="dataSource"/>
??</bean>
</beans>
提供POJO的java类：Person.javapublic?class?Person {
??private?Integer id;
??private?String name;
??
??public?Person(){}
??
??public?Person(String name) {
????this.name = name;
??}
??public?Integer getId() {
????return?id;
??}
??public?void?setId(Integer id) {
????this.id = id;
??}
??public?String getName() {
????return?name;
??}
??public?void?setName(String name) {
????this.name = name;
??}
}
提供对Person的操作接口：PersonService.javapublic?interface?PersonService {
??
??public?void?save(Person person);
??
??public?void?update(Person person);
??
??public?Person getPerson(Integer personid);
??
??public?List<Person> getPersons();
??
??public?void?delete(Integer personid)?throws?Exception;
}

提供对接口的实现类：PersonServiceBean.javapublic?class?PersonServiceBean?implements?PersonService {
??private?JdbcTemplate jdbcTemplate;
??
??public?void?setDataSource(DataSource dataSource) {
????this.jdbcTemplate =?new?JdbcTemplate(dataSource);
??}
??
??public?void?delete(Integer personid)?throws?Exception{
????jdbcTemplate.update("delete from person where id=?",?new?Object[]{personid},
????????new?int[]{java.sql.Types.INTEGER});
??}
??
??public?Person getPerson(Integer personid) {????
????return?(Person)jdbcTemplate.queryForObject("select * from person where id=?",?new?Object[]{personid},
????????new?int[]{java.sql.Types.INTEGER},?new?PersonRowMapper());
??}

??@SuppressWarnings("unchecked")
??public?List<Person> getPersons() {
????return?(List<Person>)jdbcTemplate.query("select * from person",?new?PersonRowMapper());
??}

??public?void?save(Person person) {
????jdbcTemplate.update("insert into person(name) values(?)",?new?Object[]{person.getName()},
????????new?int[]{java.sql.Types.VARCHAR});
??}

??public?void?update(Person person) {
????jdbcTemplate.update("update person set name=? where id=?",?new?Object[]{person.getName(), person.getId()},
????????new?int[]{java.sql.Types.VARCHAR, java.sql.Types.INTEGER});
??}
}
提供在查询对象时，记录的映射回调类：PersonRowMapper.javapublic?class?PersonRowMapper?implements?RowMapper {

??public?Object mapRow(ResultSet rs,?int?index)?throws?SQLException {
????Person person =?new?Person(rs.getString("name"));
????person.setId(rs.getInt("id"));
????return?person;
??}
}

【注意】：由于dbcp的jar包对common-pool和commons-collections的jar包有依赖，所有需要把他们一起引入到工程中。【?commons-dbcp-1.2.1.jar, commons-pool-1.2.jar, commons-collections-3.1.jar】, 参考文档《JDBC高级部分》：http://tianya23.blog.51cto.com/1081650/270849
2、JdbcTemplate事务事务的操作首先要通过配置文件，取得spring的支持， 再在java程序中显示的使用@Transactional注解来使用事务操作。
在xml配置文件中增加对事务的支持：<bean?id="txManager"?class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
????????????<property?name="dataSource"?ref="dataSource"/>
????????</bean>
??<tx:annotation-driven?transaction-manager="txManager"/>
??
??<bean?id="personService"?class="cn.comp.service.impl.PersonServiceBean">
????<property?name="dataSource"?ref="dataSource"/>
??</bean>
在java程序中显示的指明是否需要事务，当出现运行期异常Exception或一般的异常Exception是否需要回滚@Transactional
public?class?PersonServiceBean?implements?PersonService {
??private?JdbcTemplate jdbcTemplate;
??
??public?void?setDataSource(DataSource dataSource) {
????this.jdbcTemplate =?new?JdbcTemplate(dataSource);
??}
??// unchecked ,
??// checked
??@Transactional(noRollbackFor=RuntimeException.class)
??public?void?delete(Integer personid)?throws?Exception{
????jdbcTemplate.update("delete from person where id=?",?new?Object[]{personid},
????????new?int[]{java.sql.Types.INTEGER});
????throw?new?RuntimeException("运行期例外");
??}
??@Transactional(propagation=Propagation.NOT_SUPPORTED)
??public?Person getPerson(Integer personid) {????
????return?(Person)jdbcTemplate.queryForObject("select * from person where id=?",?new?Object[]{personid},
????????new?int[]{java.sql.Types.INTEGER},?new?PersonRowMapper());
??}

??@Transactional(propagation=Propagation.NOT_SUPPORTED)
??@SuppressWarnings("unchecked")
??public?List<Person> getPersons() {
????return?(List<Person>)jdbcTemplate.query("select * from person",?new?PersonRowMapper());
??}

??public?void?save(Person person) {
????jdbcTemplate.update("insert into person(name) values(?)",?new?Object[]{person.getName()},
????????new?int[]{java.sql.Types.VARCHAR});
??}

??public?void?update(Person person) {
????jdbcTemplate.update("update person set name=? where id=?",?new?Object[]{person.getName(), person.getId()},
????????new?int[]{java.sql.Types.VARCHAR, java.sql.Types.INTEGER});
??}
}在默认情况下，Spring会对RuntimeException异常进行回滚操作，而对Exception异常不进行回滚。可以显示的什么什么样的异常需要回滚，什么样的异常不需要回滚， 通过?@Transactional(noRollbackFor=RuntimeException.class)设置要求运行时异常不回滚 或者通过RollbackFor=Exception.class来要求需要捕获的异常回滚。
【注意】Spring对数据库的操作提供了强大的功能，比如RowMapper接口封装数据库字段与Java属性的映射、查询返回List的函数等，但是里面还要写一堆SQL语句还是比较烦人的，在这部分建议使用ibatis或hibernate来代替， 不知道Spring后期的版本会不会把这个整合到里面。