Spring @PropertySource示例

偏执的太偏执、 2023-02-15 05:14 109阅读 0赞

![弹簧属性示例][format_png]![弹簧属性示例][format_png 1]

在Spring中，您可以使用`@PropertySource`批注将您的配置外部`@PropertySource`属性文件。 在本教程中，我们将向您展示如何使用`@PropertySource`读取属性文件并使用`@Value`和`Environment`显示值。

*PS @PropertySource从Spring 3.1开始可用*

## 1. @PropertySource和@Value ##

一个经典示例，读取属性文件并显示`${}` 。

config.properties

mongodb.url=1.2.3.4
    mongodb.db=hello

AppConfigMongoDB

package com.mkyong.config;
    
    import org.springframework.beans.factory.annotation.Value;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.ComponentScan;
    import org.springframework.context.annotation.Configuration;
    import org.springframework.context.annotation.PropertySource;
    import org.springframework.context.support.PropertySourcesPlaceholderConfigurer;
    //...
    
    @Configuration
    @ComponentScan(basePackages = { "com.mkyong.*" })
    @PropertySource("classpath:config.properties")
    public class AppConfigMongoDB {
    
    	//1.2.3.4
    	@Value("${mongodb.url}")
    	private String mongodbUrl;
    
    	//hello
    	@Value("${mongodb.db}")
    	private String defaultDb;
    
    	@Bean
    	public MongoTemplate mongoTemplate() throws Exception {
    
    		MongoClientOptions mongoOptions = 
    			new MongoClientOptions.Builder().maxWaitTime(1000 * 60 * 5).build();
    		MongoClient mongo = new MongoClient(mongodbUrl, mongoOptions);
    		MongoDbFactory mongoDbFactory = new SimpleMongoDbFactory(mongo, defaultDb);
    		return new MongoTemplate(mongoDbFactory);
    
    	}
    
    	//To resolve ${} in @Value
    	@Bean
    	public static PropertySourcesPlaceholderConfigurer propertyConfigInDev() {
    		return new PropertySourcesPlaceholderConfigurer();
    	}
    
    }

> **注意**  
> 要在`@Values`解析$ \{\}，必须在XML或注释配置文件中注册静态`PropertySourcesPlaceholderConfigurer` 。

## 2. @PropertySource和环境 ##

Spring建议使用`Environment`获取属性值。

AppConfigMongoDB

package com.mkyong.config;
    
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.context.annotation.Bean;
    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.mkyong.*" })
    @PropertySource("classpath:config.properties")
    public class AppConfigMongoDB {
    
    	@Autowired
    	private Environment env;
    
    	@Bean
    	public MongoTemplate mongoTemplate() throws Exception {
    
    		String mongodbUrl = env.getProperty("mongodb.url");
    		String defaultDb = env.getProperty("mongodb.db");
    		
    		MongoClientOptions mongoOptions = 
    			new MongoClientOptions.Builder().maxWaitTime(1000 * 60 * 5).build();
    		MongoClient mongo = new MongoClient(mongodbUrl, mongoOptions);
    		MongoDbFactory mongoDbFactory = new SimpleMongoDbFactory(mongo, defaultDb);
    		return new MongoTemplate(mongoDbFactory);
    
    	}
    
    }

## 3.更多@PropertySource示例 ##

比较常见的例子。

3.1解决`@PropertySource`资源位置中的$ \{\}的示例。

@Configuration
    	@PropertySource("file:${app.home}/app.properties")
    	public class AppConfig {
    		@Autowired
    		Environment env;
    	}

在启动期间设置系统属性。

System.setProperty("app.home", "test");
    
    	java -jar -Dapp.home="/home/mkyon/test" example.jar

3.2包括多个属性文件。

@Configuration
    	@PropertySource({
    		"classpath:config.properties",
    		"classpath:db.properties" //if same key, this will 'win'
    	})
    	public class AppConfig {
    		@Autowired
    		Environment env;
    	}

> 注意  
> 如果属性键重复，则最后声明的文件将“获胜”并覆盖。

## 4. Spring 4和@PropertySources ##

Spring 4的一些增强功能。

4.1引入了新的`@PropertySources`以支持Java 8和更好的方式来包含多个属性文件。

@Configuration
    	@PropertySources({
    		@PropertySource("classpath:config.properties"),
    		@PropertySource("classpath:db.properties")
    	})
    	public class AppConfig {
    		//...
    	}

4.2允许`@PropertySource`忽略未找到的属性文件。

@Configuration
    	@PropertySource("classpath:missing.properties")
    	public class AppConfig {
    		//...
    	}

如果找不到`missing.properties` ，则系统无法启动并抛出`FileNotFoundException`

Caused by: java.io.FileNotFoundException: 
    		class path resource [missiong.properties] cannot be opened because it does not exist

在Spring 4中，您可以使用`ignoreResourceNotFound`忽略未找到的属性文件

@Configuration
    	@PropertySource(value="classpath:missing.properties", ignoreResourceNotFound=true)
    	public class AppConfig {
    		//...
    	}

@PropertySources({
    		@PropertySource(value = "classpath:missing.properties", ignoreResourceNotFound=true),
    		@PropertySource("classpath:config.properties")
            })

做完了

## 参考文献 ##

1.  [Sprong IO – PropertySource][Sprong IO _ PropertySource]
2.  [SpringIO – PropertySources][SpringIO _ PropertySources]
3.  [Spring IO –配置][Spring IO]
4.  [Spring @Value默认值][Spring _Value]
5.  [SpringJIRA：SPR-8539][SpringJIRA_SPR-8539]

标签： [春天][Link 1] [spring3][] [spring4][]

> 翻译自: [https://mkyong.com/spring/spring-propertysources-example/][https_mkyong.com_spring_spring-propertysources-example]

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[Sprong IO _ PropertySource]: http://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/context/annotation/PropertySource.html
[SpringIO _ PropertySources]: http://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/context/annotation/PropertySources.html
[Spring IO]: http://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/context/annotation/Configuration.html
[Spring _Value]: http://www.mkyong.com/spring3/spring-value-default-value/
[SpringJIRA_SPR-8539]: https://jira.spring.io/browse/SPR-8539
[Link 1]: https://mkyong.com/tag/spring/
[spring3]: https://mkyong.com/tag/spring3/
[spring4]: https://mkyong.com/tag/spring4/
[https_mkyong.com_spring_spring-propertysources-example]: https://mkyong.com/spring/spring-propertysources-example/