spring3中使用@value注解获取属性值

  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.propertiesvalue>
            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.propertiesvalue>
        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: 
  1. <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"> 
 的命名空间,然后
<bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">    
    <property name="locations">    
        <list>    
            <value>classpath:test.propertiesvalue>    
        list>                
    property>                                
bean>  
3.创建test.properties 
   abc=123 
4.读取配置文件内容
  1. 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;     
        }  
    }  
 这样就将test.abc的值注入了imageDir中了。
 

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.propertiesvalue>  
        list>  
    property>  
bean>  

最近发现这样也可以,代码更整洁:

  1. <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:

 is the XML equivalent to the PropertyPlaceholderConfigurer. So, prefer that. The  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;

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