spring 后处理器

Bean后处理器

新建maven项目并添加spring依赖，目录结构如下

Axe

public interface Axe {
    public String chop();
}

Person

public interface Person {
    public void useAxe();
}

SteelAxe

public class SteelAxe
        implements Axe
{
    public SteelAxe()
    {
        System.out.println("Spring实例化依赖bean：SteelAxe实例...");
    }
    public String chop()
    {
        return "钢斧砍柴真快";
    }
}

Chinese

public class Chinese implements Person,InitializingBean {
    private Axe axe;
    private String name;

    public Chinese() {
        System.out.println("Spring 实例化主调bean:Chinese实例...");
    }

    public void setAxe(Axe axe) {
        this.axe = axe;
    }

    public void setName(String name) {
        System.out.println("Spring执行setName()方法注入依赖关系...");
        this.name = name;
    }

    public void useAxe(){
        System.out.println(name+axe.chop());
    }

    public void init(){
        System.out.println("正在执行初始化方法init...");
    }

    public void afterPropertiesSet() throws Exception {
        System.out.println("正在执行初始化方法afterPropertiesSet...");
    }
}

MyBeanPostProcessor

package org.mythsky.springdemo;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.lang.Nullable;

public class MyBeanPostProcessor implements BeanPostProcessor {

    @Nullable
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("Bean后处理器在初始化之前对"+beanName+"进行增强处理...");
        return bean;
    }

    @Nullable
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("Bean后处理器在初始化之后对"+beanName+"进行增强处理...");
        if(bean instanceof Chinese){
            Chinese c=(Chinese)bean;
            c.setName("Hello world!");
        }
        return bean;
    }
}

测试BeanTest

package org.mythsky.springdemo;

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

public class BeanTest {
    public static void main(String[] args){
        ApplicationContext ctx=new ClassPathXmlApplicationContext("services.xml");
        Person p=(Person)ctx.getBean("chinese");
        p.useAxe();
    }
}

services.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:p="http://www.springframework.org/schema/p"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
                http://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="steelAxe" class="org.mythsky.springdemo.SteelAxe"></bean>
    <bean id="chinese" class="org.mythsky.springdemo.Chinese" init-method="init" p:axe-ref="steelAxe" p:name="依赖注入的值"></bean>
    <bean class="org.mythsky.springdemo.MyBeanPostProcessor"></bean>

</beans>

测试结果

容器后处理器

MyBeanFactoryPostProcessor

package org.mythsky.springdemo;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;

public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor {
    public void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException {
        System.out.println("程序对Spring所做的BeanFactory的初始化没有改变...");
        System.out.println("Spring容器是:"+configurableListableBeanFactory);
    }
}

services.xml

<bean class="org.mythsky.springdemo.MyBeanFactoryPostProcessor"></bean>

运行上面的测试

PropertyPlaceholderConfigurer

services.xml

<bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <property name="locations">
            <list>
                <value>dbconn.properties</value>
            </list>
        </property>
    </bean>
    <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource" destroy-method="close"
          p:driverClass="${jdbc.driverClassName}"
          p:jdbcUrl="${jdbc.url}"
          p:user="${jdbc.username}"
          p:password="${jdbc.password}"></bean>

dbconn.properties

jdbc.driverClassName=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://10.200.151.28:3306/spring
jdbc.username=root
jdbc.password=pass

MysqlTest

package org.mythsky.springdemo;

import com.mchange.v2.c3p0.ComboPooledDataSource;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MysqlTest {
    public static void main(String[] args){
        ApplicationContext ctx=new ClassPathXmlApplicationContext("services.xml");
        ComboPooledDataSource dataSource= (ComboPooledDataSource) ctx.getBean("dataSource");
        System.out.println(dataSource.getDriverClass());
        System.out.println(dataSource.getJdbcUrl());
        System.out.println(dataSource.getUser());
        System.out.println(dataSource.getPassword());
    }
}

添加c3p0依赖

<dependency>
            <groupId>com.mchange</groupId>
            <artifactId>c3p0</artifactId>
            <version>0.9.5.2</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.-dmr</version>
        </dependency>

运行结果

PropertyOverrideConfigurer

services.xml

    <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource" destroy-method="close"
          p:driverClass="${jdbc.driverClassName}"
          p:jdbcUrl="${jdbc.url}"
          p:user="${jdbc.username}"
          p:password="${jdbc.password}"></bean>
    <bean class="org.springframework.beans.factory.config.PropertyOverrideConfigurer">
        <property name="locations">
            <list>
                <value>db.properties</value>
            </list>
        </property>
    </bean>
    <bean id="dataSource2" class="com.mchange.v2.c3p0.ComboPooledDataSource" destroy-method="close"></bean>

db.properties

dataSource2.driverClass=com.mysql.jdbc.Driver
dataSource2.jdbcUrl=jdbc:mysql://10.200.151.28:3306/spring
dataSource2.user=root
dataSource2.password=pass

MysqlTest

ComboPooledDataSource dataSource= (ComboPooledDataSource) ctx.getBean("dataSource2");

运行结果同上。

以上两种配置可以简写

<context:property-placeholder location="dbconn.properties"></context:property-placeholder>
    <context:property-override location="db.properties"></context:property-override>