Null return value from advice does not match primitive

Posted 2021-02-12 fanling521

Exception in thread "main" org.springframework.aop.AopInvocationException: Null return value from advice does not match primitive return type for: public int com.fanling.xmlaop.UserDaoImpl.addUser(com.fanling.xmlaop.User)
	at org.springframework.aop.framework.CglibAopProxy.processReturnType(CglibAopProxy.java:391)
	at org.springframework.aop.framework.CglibAopProxy.access$000(CglibAopProxy.java:84)
	at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:690)

这个错就是返回的类型不匹配。

造成的原因：

目标类的方法有返回值，而around环绕方法没有返回值

解决方法

CglibAopProxy.java类

@Nullable
    private static Object processReturnType(Object proxy, @Nullable Object target, Method method, @Nullable Object returnValue) {
        if (returnValue != null && returnValue == target && !RawTargetAccess.class.isAssignableFrom(method.getDeclaringClass())) {
            returnValue = proxy;
        }

        Class<?> returnType = method.getReturnType();
        if (returnValue == null && returnType != Void.TYPE && returnType.isPrimitive()) {
            throw new AopInvocationException("Null return value from advice does not match primitive return type for: " + method);
        } else {
            return returnValue;
        }
    }

方法1：将int 改为包装类型不报错

方法2：修改around的方法，修改为Object返回类型

    public Object around(ProceedingJoinPoint pjt ){
        Object object = null;
        try {
            System.out.println("环绕通知");
            object= pjt.proceed();
        } catch (Throwable throwable) {
            throwable.printStackTrace();
        }
        return object;
    }