在spring 3.0中，可以通过使用@value，对一些如xxx.properties文件中的文件，进行键值对的注入。
@Value有两种使用方式：@Value("#{configProperties['t1.msgname']}")或者@Value("${t1.msgname}")；
其次，下面我们来看看如何使用这两形式，在配置上有什么区别：
1、@Value("#{configProperties['t1.msgname']}")这种形式的配置中有“configProperties”，其实它指定的是配置文件的加载对象：配置如下：
<bean id="configProperties" class="org.springframework.beans.factory.config.PropertiesFactoryBean"> <property name="locations"> <list> <value>classpath:/config/t1.properties</value> </list> </property> </bean>
这样配置就可完成对属性的具体注入了；
2、@Value("${t1.msgname}")这种形式不需要指定具体加载对象，这时候需要一个关键的对象来完成PreferencesPlaceholderConfigurer，这个对象的配置可以利用上面配置1中的配置，也可以自己直接自定配置文件路径。
如果使用配置1中的配置，可以写成如下情况：
<bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PreferencesPlaceholderConfigurer"> <property name="properties" ref="configProperties"/> </bean>
如果直接指定配置文件的话，可以写成如下情况：
<bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PreferencesPlaceholderConfigurer"> <property name="location"> <value>config/t1.properties</value> </property> </bean>
如果使用注解，可以写成如下情况：
@Configuration @ComponentScan(basePackages = "com.dxz.config") public class ServiceConfiguration2 { public ServiceConfiguration2() { System.out.println("ServiceConfiguration zheli"); } @Bean public static PropertyPlaceholderConfigurer configurer() { PropertyPlaceholderConfigurer ppc = new PropertyPlaceholderConfigurer(); Resource resources = new ClassPathResource( "spring/config.properties" ); ppc.setLocation(resources); return ppc; } @Bean public Configs2 configs2(@Value("${ds.user}") String user, @Value("${key1}") String key1) { Configs2 configs = new Configs2(); configs.setApiKeyId(user); configs.setSecretApiKey(key1); System.out.println("in ServiceConfiguration" + configs); return configs; }
}
示例1：xml中配置PropertyPlaceholderConfigurer
1.首先在applicationContext.xml中加入：
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<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-3.0.xsd">
<bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"> <property name="locations"> <list> <value>classpath:test.properties</value> </list> </property> </bean>
abc=123
4.读取配置文件内容
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import org.springframework.beans.factory.annotation.Value; import org.springframework.stereotype.Controller; import org.springframework.web.bind.annotation.RequestMapping; @RequestMapping("/admin/images") @Controller public class ImageAdminController { private String imageDir; @Value("${abc}") public void setImageDir(String val) { this.imageDir = val; } }
示例2：context:property-placeholder
有时候需要从properties文件中加载配置，以前的方式是这样的：
<bean id="jdbcProperties" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"> <property name="locations"> <list> <value>classpath*:/spring/jdbc.properties</value> </list> </property> </bean>
最近发现这样也可以，代码更整洁：
-
<context:property-placeholder location="classpath:spring/jdbc.properties" />
在bean定义中依然可以通过“${}”这种方式来去值：
<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource"> <property name="driverClassName" value="${jdbc.driverClassName}" /> <property name="url" value="${jdbc.url}" /> <property name="username" value="${jdbc.username}" /> <property name="password" value="${jdbc.password}" /> <property name="initialSize" value="${jdbc.initialSize}" /> <property name="maxActive" value="${jdbc.maxActive}" /> <property name="maxIdle" value="${jdbc.maxIdle}" /> <property name="minIdle" value="${jdbc.minIdle}" /> </bean>
说明：
<context:property-placeholder ... /> is the XML equivalent to the PropertyPlaceholderConfigurer. So, prefer that. The <util:properties/> simply factories a java.util.Properties instance that you can inject.
示例3：@PropertySource + Environment
在spring3.1中（不是spring3.0）还可以这样：
package com.dxz.config; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.context.annotation.ComponentScan; import org.springframework.context.annotation.Configuration; import org.springframework.context.annotation.PropertySource; import org.springframework.core.env.Environment; @Configuration @ComponentScan(basePackages = "com.dxz.config") @PropertySource(value = "classpath:spring/config.properties") public class ServiceConfiguration { @Autowired Environment environment; public ServiceConfiguration() { System.out.println("ServiceConfiguration zheli"); } //@Bean public javax.sql.DataSource dataSource(){ String user = this.environment.getProperty("ds.user"); System.out.println(user); return null; } }
配置文件config.properties：
key1=abc key2=aaaaaaaaaaaaaaaaaaaa key3=bbbbbbbbbbbbbbbbbbbbbbbbbbb key4=cccccccccc ds.user=admin
测试类：
package com.dxz.config; import org.springframework.context.ApplicationContext; import org.springframework.context.annotation.AnnotationConfigApplicationContext; public class Test { public static void main(String[] args) { ApplicationContext context = new AnnotationConfigApplicationContext(ServiceConfiguration.class); ServiceConfiguration hc2 = (ServiceConfiguration) context.getBean("serviceConfiguration"); hc2.dataSource(); } }
结果：
十一月 02, 2017 10:20:43 上午 org.springframework.context.annotation.AnnotationConfigApplicationContext prepareRefresh 信息: Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@3f91beef: startup date [Thu Nov 02 10:20:43 CST 2017]; root of context hierarchy ServiceConfiguration zheli admin
说明：
In Spring 3.0, you can "access" properties defined using the PropertyPlaceHolderConfigurer mechanism using the SpEl annotations:
PropertyPlaceHolderConfigurer可以在xml中配置，如上面提过的。
@Value("${ds.user}")
private String user;
If you want to remove the XML all together, simply register the PropertyPlaceholderConfigurer manually using Java configuration. I prefer the 3.1 approach. But, if youre using the Spring 3.0 approach (since 3.1's not GA yet...), you can now define the above XML like this:
如果不采用xml配置，在java编码配置中可以用如下的注册方式来注册PropertyPlaceholderConfigurer，如下
示例4： PropertyPlaceholderConfigurer + @Value
package com.dxz.config; import org.springframework.beans.factory.annotation.Value; import org.springframework.beans.factory.config.PropertyPlaceholderConfigurer; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.ComponentScan; import org.springframework.context.annotation.Configuration; import org.springframework.core.io.ClassPathResource; import org.springframework.core.io.Resource; @Configuration @ComponentScan(basePackages = "com.dxz.config") public class ServiceConfiguration2 { public ServiceConfiguration2() { System.out.println("ServiceConfiguration zheli"); } @Bean public static PropertyPlaceholderConfigurer configurer() { PropertyPlaceholderConfigurer ppc = new PropertyPlaceholderConfigurer(); Resource resources = new ClassPathResource( "spring/config.properties" ); ppc.setLocation(resources); return ppc; } @Bean public Configs2 configs2(@Value("${ds.user}") String user, @Value("${key1}") String key1) { Configs2 configs = new Configs2(); configs.setApiKeyId(user); configs.setSecretApiKey(key1); System.out.println("in ServiceConfiguration" + configs); return configs; } }
package com.dxz.config; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Service; @Service public class TestConfigs2 { @Autowired Configs2 configs2; @Autowired Configs configs; public void testConfigs2() { System.out.println("configs:"+configs.getApiKeyId()); System.out.println("configs2:"+configs2.getApiKeyId()); } }
package com.dxz.config; import org.springframework.beans.factory.annotation.Value; import org.springframework.stereotype.Component; @Component public class Configs { @Value("${key1}") public String apiKeyId; @Value("${ds.user}") public String secretApiKey; public String getApiKeyId() { return apiKeyId; } public String getSecretApiKey() { return secretApiKey; } } package com.dxz.config; //@Component public class Configs2 { public String apiKeyId; public String secretApiKey; public String getApiKeyId() { return apiKeyId; } public void setApiKeyId(String apiKeyId) { this.apiKeyId = apiKeyId; } public String getSecretApiKey() { return secretApiKey; } public void setSecretApiKey(String secretApiKey) { this.secretApiKey = secretApiKey; } @Override public String toString() { return "Configs2 [apiKeyId=" + apiKeyId + ", secretApiKey=" + secretApiKey + "]"; } }
测试类：
package com.dxz.config; import org.springframework.context.ApplicationContext; import org.springframework.context.annotation.AnnotationConfigApplicationContext; public class Test { public static void main(String[] args) { ApplicationContext context = new AnnotationConfigApplicationContext(ServiceConfiguration2.class); TestConfigs2 hc2 = (TestConfigs2) context.getBean("testConfigs2"); hc2.testConfigs2(); } }
结果：
ServiceConfiguration zheli ServiceConfiguration zheli in ServiceConfigurationConfigs2 [apiKeyId=admin, secretApiKey=abc] configs:abc configs2:admin
说明：
1、static类型的会优先在spring容器中注册。Note that the PPC is defined using a static bean definition method. This is required to make sure the bean is registered early, because the PPC is a BeanFactoryPostProcessor - it can influence the registration of the beans themselves in the context, so it necessarily has to be registered before everything else.
2、上面示例中有2中场景：
configs是spring容器管理的bean，configs的成员变量通过@Value注解获取配置文件的配置值；
configs2是普通的pojo类，没有注册到spring容器中，在初始化时，通过其创建方法中通过@Value注解获取传入配置文件中的配置值；
不要忘记这时候需要一个关键的对象来完成PreferencesPlaceholderConfigurer来支持；