spring 自定义让@Value被解析到

//自动注入此对象

  @Autowired

     private Environment environment;

     @PostConstruct

     public void init() {

        //拿到些对象

         MutablePropertySources propertySources = ((ConfigurableEnvironment) this .environment).getPropertySources();

         PropertySourceFactory factory = BeanUtils.instantiateClass(DefaultPropertySourceFactory. class );

         //构造pathResource

         PathResource pathResource = new PathResource( "/Users/xx/soft/sp.properties" );

         try {

             org.springframework.core.env.PropertySource<?> sd = factory.createPropertySource( "sd" , new EncodedResource(pathResource));

             //设置值

             propertySources.addFirst(sd);

         } catch (IOException e) {

             e.printStackTrace();

         }

     }

import org.springframework.stereotype.Service;

/**

  * 测试Bean

  */

@Service ( "userService" )

public class UserService {

  public int count() {

   return 10 ;

  }

  public int max( int size) {

   int count = count();

   return count > size ? count : size;

  }

}

import org.springframework.beans.factory.InitializingBean;

import org.springframework.beans.factory.annotation.Value;

import org.springframework.stereotype.Component;

@Component

public class AppRunner implements InitializingBean {

  /**

   * 引用一个配置项

   */

  @Value ( "${app.port}" )

  private int port;

  /**

   * 调用容器的一个bean的方法获取值

   */

  @Value ( "#{userService.count()}" )

  private int userCount;

  /**

   * 调用容器的一个bean的方法，且传入一个配置项的值作为参数

   */

  @Value ( "#{userService.max(${app.size})}" )

  private int max;

  /**

   * 简单的运算

   */

  @Value ( "#{${app.size} <= '12345'.length() ? ${app.size} : '12345'.length()}" )

  private int min;

  //测试

  public void afterPropertiesSet() throws Exception {

   System.out.println( "port : " + port);

   System.out.println( "userCount : " + userCount);

   System.out.println( "max : " + max);

   System.out.println( "min : " + min);

  }

}

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

import org.springframework.context.annotation.ComponentScan;

import org.springframework.context.annotation.PropertySource;

@ComponentScan

@PropertySource ( "classpath:app.properties" )

public class App {

     public static void main( String[] args) {

      AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(App. class );

      context.close();

     }

}

import org.springframework.beans.factory.config.BeanExpressionContext;

import org.springframework.beans.factory.config.BeanExpressionResolver;

import org.springframework.beans.factory.config.ConfigurableBeanFactory;

import org.springframework.context.expression.StandardBeanExpressionResolver;

public class ValueUtil {

  private static final BeanExpressionResolver resolver = new StandardBeanExpressionResolver();

  /**

   * 解析一个表达式，获取一个值

   * @param beanFactory

   * @param value 一个固定值或一个表达式。如果是一个固定值，则直接返回固定值，否则解析一个表达式，返回解析后的值

   * @return

   */

  public static Object resolveExpression(ConfigurableBeanFactory beanFactory, String value) {

   String resolvedValue = beanFactory.resolveEmbeddedValue(value);

   if (!(resolvedValue.startsWith( "#{" ) && value.endsWith( "}" ))) {

    return resolvedValue;

   }

   return resolver.evaluate(resolvedValue, new BeanExpressionContext(beanFactory, null ));

  }

}

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

import org.springframework.context.annotation.ComponentScan;

import org.springframework.context.annotation.PropertySource;

@ComponentScan

@PropertySource ( "classpath:app.properties" )

public class App {

     public static void main( String[] args) {

      AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(App. class );

      //计算一个具体的值（非表达式）

      System.out.println(ValueUtil.resolveExpression(context.getBeanFactory(), "1121" ));

      //实现@Value的功能

      System.out.println(ValueUtil.resolveExpression(context.getBeanFactory(), "${app.port}" ));

      System.out.println(ValueUtil.resolveExpression(context.getBeanFactory(), "#{userService.count()}" ));

      System.out.println(ValueUtil.resolveExpression(context.getBeanFactory(), "#{userService.max(${app.size})}" ));

      System.out.println(ValueUtil.resolveExpression(context.getBeanFactory(), "#{${app.size} <= '12345'.length() ? ${app.size} : '12345'.length()}" ));

      context.close();

     }

}

@Retention (RUNTIME)

@Target (TYPE)

public @interface Job {

  String cron();

}

@Job (cron = "0 0 12 * * ?" )

@Job (cron = "${app.job.cron}" )