一:说明

Spring EL-Spring表达式语言，支持在xml和注解中使用表达式，类似于JSP的EL表达式语言。

Spring 开发中经常涉及调用各种资源的情况，包含普通文件，网址，配置文件，系统环境变量等。我们可以使用Spring的表达式语言实现资源的注入。

二：代码实例

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@Configuration
@ComponentScan("com.gemdale")
@PropertySource("classpath:com/gemdale/gmap/spring/boot/demo/el/test.properties")
public class ElConfig {
@Value("I love youe!")
private String normal;
@Value("#{systemProperties['os.name']}")
private String osName;
@Value("#{ T(java.lang.Math).random() * 100.0 }")
private double randomNumber;
@Value("#{demoService.another}")
private String fromAnother;
@Value("classpath:com/gemdale/gmap/spring/boot/demo/el/test.txt")
private Resource testFile;
@Value("http://www.baidu.com")
private Resource testUrl;
@Value("${book.name}")
private String bookName;
@Autowired
private Environment environment;
@Bean
public static PropertySourcesPlaceholderConfigurer propertyConfigure() {
return new PropertySourcesPlaceholderConfigurer();
}
public void outputResource() {
try {
System.out.println(normal);
System.out.println(osName);
System.out.println(randomNumber);
System.out.println(fromAnother);
System.out.println(IOUtils.toString(testFile.getInputStream()));
System.out.println(IOUtils.toString(testUrl.getInputStream()));
System.out.println(bookName);
System.out.println(environment.getProperty("book.author"));
}
catch (Exception e) {
e.printStackTrace();
}
}
}

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public class Start {
public static void main(String[] args) throws Exception {
AnnotationConfigApplicationContext configApplicationContext = new AnnotationConfigApplicationContext(
ElConfig.class);
ElConfig resourceService = configApplicationContext.getBean(ElConfig.class);
resourceService.outputResource();
configApplicationContext.close();
}
}

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ITPub博客

Spring EL