Spring 使用外部屬性文件

Spring 使用外部屬性文件

一、說在前面

在配置文件裏配置 bean 時，有時需要在 Bean 的配置裏混入系統部署的細節信息(例如: 文件路徑, 數據源配置信息等)，而這些部署細節實際上需要和 bean配置相分離。

Spring 提供了一個 PropertyPlaceholderConfigurer 的 BeanFactory 後置處理器, 這個處理器允許用戶將 Bean 配置的部分內容外移到屬性文件中。 可以在 Bean 配置文件裏使用形式爲 ${xxx} 的變量, PropertyPlaceholderConfigurer 從屬性文件里加載屬性, 並使用這些屬性來替換變量。

二、以數據庫配置爲例

1、beans-properties.xml配置文件

<?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"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd">
	
	<!-- 導入屬性文件 -->
	<context:property-placeholder location="classpath:db.properties"/>
	
	<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
		<!-- 使用外部的屬性文件的屬性 -->
		<property name="user" value="${user}"></property>
		<property name="password" value="${password}"></property>
		<property name="driverClass" value="${driverClass}"></property>
		<property name="jdbcUrl" value="${jdbcUrl}"></property>
	</bean>

</beans>

2、db.properties屬性文件

user=root
password=111111
driverClass=com.mysql.jdbc.Driver
jdbcUrl=jdbc:mysql:///spring

3、測試函數

package com.at.beans.properties;

import java.sql.SQLException;

import javax.sql.DataSource;

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

public class TestProperties {

	public static void main(String[] args) throws SQLException {
		ApplicationContext ctx = new ClassPathXmlApplicationContext("beans-properties.xml");
		DataSource dataSource = (DataSource) ctx.getBean("dataSource");
		System.out.println(dataSource.getConnection());
		/*System.out.println(dataSource.getConnection("root", "111111"));*/
	}
}

4、輸出結果

五月 23, 2017 8:21:29 下午 org.springframework.context.support.AbstractApplicationContext prepareRefresh
信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@218fcdce: startup date [Tue May 23 20:21:28 CST 2017]; root of context hierarchy
五月 23, 2017 8:21:29 下午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
信息: Loading XML bean definitions from class path resource [beans-properties.xml]
五月 23, 2017 8:21:29 下午 org.springframework.core.io.support.PropertiesLoaderSupport loadProperties
信息: Loading properties file from class path resource [db.properties]
五月 23, 2017 8:21:29 下午 com.mchange.v2.log.MLog <clinit>
信息: MLog clients using java 1.4+ standard logging.
五月 23, 2017 8:21:29 下午 com.mchange.v2.c3p0.C3P0Registry banner
信息: Initializing c3p0-0.9.1.2 [built 21-May-2007 15:04:56; debug? true; trace: 10]
五月 23, 2017 8:21:30 下午 com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource getPoolManager
信息: Initializing c3p0 pool... com.mchange.v2.c3p0.ComboPooledDataSource [ acquireIncrement -> 3, acquireRetryAttempts -> 30, acquireRetryDelay -> 1000, autoCommitOnClose -> false, automaticTestTable -> null, breakAfterAcquireFailure -> false, checkoutTimeout -> 0, connectionCustomizerClassName -> null, connectionTesterClassName -> com.mchange.v2.c3p0.impl.DefaultConnectionTester, dataSourceName -> 1hgecch9oery6778hvxyv|7e0d5447, debugUnreturnedConnectionStackTraces -> false, description -> null, driverClass -> com.mysql.jdbc.Driver, factoryClassLocation -> null, forceIgnoreUnresolvedTransactions -> false, identityToken -> 1hgecch9oery6778hvxyv|7e0d5447, idleConnectionTestPeriod -> 0, initialPoolSize -> 3, jdbcUrl -> jdbc:mysql:///spring, maxAdministrativeTaskTime -> 0, maxConnectionAge -> 0, maxIdleTime -> 0, maxIdleTimeExcessConnections -> 0, maxPoolSize -> 15, maxStatements -> 0, maxStatementsPerConnection -> 0, minPoolSize -> 3, numHelperThreads -> 3, numThreadsAwaitingCheckoutDefaultUser -> 0, preferredTestQuery -> null, properties -> {user=******, password=******}, propertyCycle -> 0, testConnectionOnCheckin -> false, testConnectionOnCheckout -> false, unreturnedConnectionTimeout -> 0, usesTraditionalReflectiveProxies -> false ]
com.mchange.v2.c3p0.impl.NewProxyConnection@8a93430

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