spring PropertyPlaceholderConfigurer分析，带实例

墨蓝 2022-10-22 07:50 156阅读 0赞

## 1：写在前面 ##

该类的作用是替换配置文件中配置的占位符信息为properties文件中实际的值，原理是PropertyPlaceholderConfigurer实现了[BeanFactoryPostProcessor][]接口，利用其在创建bean前能够修改BeanDefinition的特点，来替换修改占位符为properties文件中的实际值。另外，关于该类的源码分析可以参考[这里][Link 1]。在spring中还一个类[PropertyOverrideConfiguer][],功能类似，感兴趣的朋友也可以看下。

## 2：例子 ##

### 2.1：定义bean ###

public class MyPropertyPlaceholderConfigurerBean { 
        private String name;
        private int age;
    
        public String getName() { 
            return name;
        }
    
        public void setName(String name) { 
            this.name = name;
        }
    
        public int getAge() { 
            return age;
        }
    
        public void setAge(int age) { 
            this.age = age;
        }
    
        @Override
        public String toString() { 
            return JSON.toJSONString(this);
        }
    }

### 2.2：xml和配置文件 ###

*  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" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
        <bean id="propertyPlaceholderConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
            <property name="location" value="classpath:studyhelp/testpropertyplaceholderconfigurer.properties"/>
            <property name="fileEncoding" value="UTF-8"/>
        </bean>
    
        <bean class="yudaosourcecode.studyhelp.MyPropertyPlaceholderConfigurerBean" id="myPropertyPlaceholderConfigurerBean">
            <property name="name" value="${my.name}"/>
            <property name="age" value="${my.age}"/>
        </bean>
    </beans>

*  配置文件

my.name=张三的歌
    my.age=900

*  测试

@Test
    public void testpropertyplaceholderconfigurer() { 
        ClassPathXmlApplicationContext ac
                = new ClassPathXmlApplicationContext("classpath*:studyhelp/testpropertyplaceholderconfigurer.xml");
        System.out.println(ac.getBean("myPropertyPlaceholderConfigurerBean"));
    }

*  运行

{"age":900,"name":"张三的歌"}
    
    Process finished with exit code 0

[BeanFactoryPostProcessor]: https://blog.csdn.net/wang0907/article/details/115440135
[Link 1]: https://blog.csdn.net/wang0907/article/details/115483144
[PropertyOverrideConfiguer]: https://blog.csdn.net/wang0907/article/details/115527684