SpEL结合AOP示例

AOP不用多说，是spring框架的两大基石之一。SpEL是Spring Expression Language的缩写，意为Spring表达式语言，，其支持在运行时查询和操作对象图提供了更加丰富的功能，最特别的是方法调用与字符串模板功能。熟悉js的es6语法的小伙伴都知道，模板字符串，这个spel就类似js的模板字符串。

本次代码主要是熟悉使用语法，并布对应实际的应场景。

一、自定义注解

java 复制代码

@Target({ElementType.PARAMETER,ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface TestAopAnn {

    /**
     * spEL
     * @return
     */
    String  spEL() default "";
}

二、自定义切面

java 复制代码

@Aspect
@Component
public class TestAopAspect {
    private final static Logger LOGGER = LoggerFactory.getLogger(TestAopAspect.class);
    
    @Pointcut("@annotation(org.example.boot3.aop.TestAopAnn)")
    public void pointCut(){}

    
    @AfterReturning(value = "pointCut()",returning = "result")
    public   void  doAfter(JoinPoint joinPoint,Object result){
        Method method = getMethod(joinPoint);
        TestAopAnn annotation = method.getAnnotation(TestAopAnn.class);
        if(annotation!=null){
            LOGGER.info("TestAopAspect-->doAfter-------后置织入");
          /// 通过spel表达式获取到形参的中name的值
            String value =getValue(joinPoint, method, annotation.spEL());
            LOGGER.info("TestAopAspect-->doBefore-------value={}",value);
             /// 将name追加到返回的list
            try {
                if(result!=null && result instanceof List){
                   List  list = (List) result;
                   list.add(value);
                }
     
            } catch (Exception e) {
                e.fillInStackTrace();
            }
        }
    }
    

    private   Method  getMethod(JoinPoint  joinPoint) {
        Signature signature = joinPoint.getSignature();
        MethodSignature methodSignature = (MethodSignature) signature;
        return methodSignature.getMethod();
    }

   /**解析spel*/
    private String  getValue(JoinPoint  joinPoint,  Method method,String elStr){
        StandardEvaluationContext context = new StandardEvaluationContext();
        DefaultParameterNameDiscoverer parameterNameDiscoverer = new DefaultParameterNameDiscoverer();
        /// 方法参数名称
        String[] parameterNames = parameterNameDiscoverer.getParameterNames(method);
        Assert.isTrue(parameterNames!=null,"参数列表不能为空");
        ///方法参数值
        Object[] args = joinPoint.getArgs();
        for (int i = 0; i < parameterNames.length; i++) {
            context.setVariable(parameterNames[i],args[i]);
        }
        ExpressionParser parser = new SpelExpressionParser();
        Expression expression = parser.parseExpression(elStr);
        return (String) expression.getValue(context);
    }
}

三、测试接口

java 复制代码

public class TestReqVO {

    private String  name;

    private String  remark;
}

java 复制代码

@RestController
@RequestMapping("/api")
public class RestApi {
    /**
     * SpEL 调用对象方法
     * @param vo
     * @return
     */
    @GetMapping("/testSpEL1")
    @TestAopAnn(spEL = "#vo.getName()")
    public List<String> getSpELList1(TestReqVO vo){
        String[] arr = { "C" ,"C++","JAVA","GoLang","Rust","Python"};
        return new ArrayList<>(Arrays.stream(arr).toList());
    }

    /**
     * SpEL 调用对象属性
     * @param vo
     * @return
     */
    @GetMapping("/testSpEL2")
    @TestAopAnn(spEL = "#vo.name")
    public List<String> getSpELList2(TestReqVO vo){
        String[] arr = { "C" ,"C++","JAVA","GoLang","Rust","Python"};
        return  new ArrayList<>(Arrays.stream(arr).toList());
    }


    @GetMapping("/fluxList")
    public Flux<List<String>> getSpEL2(){
        String[] arr = { "C" ,"C++","JAVA","GoLang","Rust","Python"};
        ArrayList<String> list = new ArrayList<>(Arrays.asList(arr));
        return Flux.just(list);
    }
    
}