8 -- 深入使用Spring -- 1...4 属性占位符配置器

<?xml version="1.0" encoding="UTF-8"?>
<!-- Spring 配置文件的根元素，使用Spring-beans-4.0.xsd语义约束 -->
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://www.springframework.org/schema/beans" 
    xmlns:context="http://www.springframework.org/schema/context"
    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">

    <bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <property name="locations">
            <list>
                <value>dbconn.properties</value>
                <!-- 如果有多个属性文件，依次在下面列出来 -->
                <!-- <value>wawa.properties</value> -->
            </list>
        </property>
    </bean>
    
    <!-- 对于采用基于XML Schema的配置文件而言，如果导入了context：命名空间，则可采用如下方式来配置该属性占位符 -->
    <!-- <context:property-placeholder location="classpath:wawa.properties"/> -->

    <!-- 定义数据源Bean，使用C3P0数据源实现 -->
    <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"
        destroy-method="close">
        <!-- Spring容器将从PropertyPlaceholderConfigurer指定的属性文件中搜索这些key对应的value，并为该Bean的属性值设置这些value值 -->
        <property name="driverClass" value="${jdbc.driverClassName}" />
        <property name="jdbcUrl" value="${jdbc.url}" />
        <property name="user" value="${jdbc.username}" />
        <property name="password" value="${jdbc.password}" />
    </bean>

</beans>

jdbc.driverClassName=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/spring
jdbc.username=root
jdbc.password=system

package edu.pri.lime._8_1_4.main;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;

import javax.sql.DataSource;

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

public class Main {
    public static void main(String[] args) {
        ApplicationContext ctx = new ClassPathXmlApplicationContext("app_8_1_4.xml");
        DataSource ds = null;
        PreparedStatement pstmt = null;
        Connection conn = null;
        try {
            ds = ctx.getBean("dataSource",DataSource.class);
            conn = ds.getConnection();
            pstmt = conn.prepareStatement("insert into news_inf values(null,?,?)");
            pstmt.setString(1, "lime");
            pstmt.setString(2, "Oracle");
            pstmt.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }finally{
            if(pstmt != null)
                try {
                    pstmt.close();
                } catch (SQLException e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                }
            if(conn != null)
                try {
                    conn.close();
                } catch (SQLException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
        }
    }
}