做一个合格的程序猿之浅析Spring IoC源码（五）再谈BeanPostProcessor(2)
上一节，我们已经初步知道了beanPostProcessor这个接口是干什么的了，可以做什么样的事情，并且我们举了一个简单的“Teacher”的例子，但是大家也有点疑问，这个实际意义是什么呢？在项目中实际运用是什么呢？
下面再给出一个例子，在实际项目中，我们一个项目一套代码，有生产环境和开发环境，数据库链接配置文件有2种，jdbc_dev.properties和jdbc_prd.properties这2个配置文件，我们只需要简单的修改一下，spring的配置文件就可以很快的切换数据源，这样支持多环境数据切换，我们就可以用BeanPostProcessor这个接口去实现
代码如下：
DataSourceConnection.java
package org.study.spring.beanpostprocessor;
public class DataSourceConnection{
private String driver;
private String jdbcName;
private String password;
private String url;
/**
* 这里得出数据库链接的各个属性
*/
public void initConnection(){
System.out.println("I am database connection ,and I get connection by dirver :"+driver+" and jdbcName :"+jdbcName+" and password:"+password);
}
public DataSourceConnection() {
}
public DataSourceConnection(String driver, String jdbcName,
String password, String url) {
this.driver = driver;
this.jdbcName = jdbcName;
this.password = password;
this.url = url;
}
public String getUrl() {
return url;
}
public void setUrl(String url) {
this.url = url;
}
public String getDriver() {
return driver;
}
public void setDriver(String driver) {
this.driver = driver;
}
public String getJdbcName() {
return jdbcName;
}
public void setJdbcName(String jdbcName) {
this.jdbcName = jdbcName;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
}
ChangeConfigSupportMultiEnvironment.java
package org.study.spring.beanpostprocessor;
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
public class ChangeConfigSupportMultiEnvironment implements BeanPostProcessor{
/**
* 目前所属的环境是dev还是prd
*/
private String devlocation;
private String configName;
public String getDevlocation() {
return devlocation;
}
public void setDevlocation(String devlocation) {
this.devlocation = devlocation;
}
public String getConfigName() {
return configName;
}
public void setConfigName(String configName) {
this.configName = configName;
}
public Object postProcessBeforeInitialization(Object bean, String beanName)
throws BeansException {
/**
* 如果该类是DataSourceConnection
*/
if(bean instanceof DataSourceConnection){
if(configName.contains("${")&&configName.contains("}")){
configName = configName.substring(0,configName.indexOf("${")).concat(devlocation);
Properties prop = new Properties();
InputStream in = Object.class.getResourceAsStream("/"+configName+".properties");
try {
prop.load(in);
} catch (IOException e) {
e.printStackTrace();
}
DataSourceConnection dsc = (DataSourceConnection)bean;
String driver = dsc.getDriver();
String jdbcName = dsc.getJdbcName();
String password = dsc.getPassword();
String url = dsc.getUrl();
if(driver.contains("${")&&driver.contains("}")){
driver = driver.replace("${", "").replace("}", "");
}
if(jdbcName.contains("${")&&jdbcName.contains("}")){
jdbcName = jdbcName.replace("${", "").replace("}", "");
}
if(password.contains("${")&&password.contains("}")){
password = password.replace("${", "").replace("}", "");
}
if(url.contains("${")&&url.contains("}")){
url = url.replace("${", "").replace("}", "");
}
driver = prop.getProperty(driver);
jdbcName = prop.getProperty(jdbcName);
password = prop.getProperty(password);
url = prop.getProperty(url);
return new DataSourceConnection(driver,jdbcName,password,url);
}
}
return bean;
}
public Object postProcessAfterInitialization(Object bean, String beanName)
throws BeansException {
// System.out.println("after..."+this.devlocation);
// System.out.println("after..."+this.configName);
return bean;
}
}
jdbc_dev.properties
jdbc.driver= com.mysql.jdbc.Driver jdbc.url= jdbc:mysql:/127.0.0.1:3306/gms?useUnicode=true&characterEncoding=UTF-8&allowMultiQueries=true jdbc.username= dev_user jdbc.password= dev_passwordjdbc_prd.properties
jdbc.driver = com.mysql.jdbc.Driver jdbc.url = jdbc:mysql:/prd.com:3306/gms?useUnicode=true&characterEncoding=UTF-8&allowMultiQueries=true jdbc.username = prd_user jdbc.password = prd_user
bean-post-processor.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:mybatis-spring="http://mybatis.org/schema/mybatis-spring"
xmlns:tx="http://www.springframework.org/schema/tx" xmlns:jee="http://www.springframework.org/schema/jee"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd
http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-3.2.xsd
http://mybatis.org/schema/mybatis-spring http://mybatis.org/schema/mybatis-spring-1.2.xsd
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.2.xsd">
<bean id="changeConfigSupportMultiEnvironment" class="org.study.spring.beanpostprocessor.ChangeConfigSupportMultiEnvironment">
<property name="devlocation" value="prd"/>
<property name="configName" value="jdbc_${environment}"/>
</bean>
<bean id="dataSourceConnection" class="org.study.spring.beanpostprocessor.DataSourceConnection">
<property name="driver" value="${jdbc.driver}"/>
<property name="jdbcName" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>
<property name="url" value="${jdbc.url}"/>
</bean>
</beans>
ChangeConfigSupportMultiEnvironmentTest.java
package org.study.spring.beanpostprocessor;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class ChangeConfigSupportMultiEnvironmentTest{
@Test
public void test2() throws Exception{
ApplicationContext applicationContext = new ClassPathXmlApplicationContext("bean-post-processor.xml");
DataSourceConnection dataSourceConnection = applicationContext.getBean("dataSourceConnection",DataSourceConnection.class);
dataSourceConnection.initConnection();
}
}
当bean-post-processor.xml中devlocation的值设置为prd，运行截图是：
设置为dev，运行截图是：
这样就可以简单的切换开发环境了，可以根据这个思想，我们可以在开发过程中，灵活的运用spring的BeanPostProcessor~