java - Spring AOP 中 @DeclareParents 注解中的泛型类型

Question

我正在尝试使用 spring aop 在 Spring 框架的一个方面使用通用接口(interface)和通用类，我想为任何用 @EntityController 注释的类设置父接口(interface):

@Component
@MongoProfile
@Aspect
public class EntityMongoControllerAspect<T> {

    @DeclareParents(value="@EntityController *",defaultImpl=EntityMongoController.class)
    private IEntityController<T> iEntityController;
}

但是 eclipse 总是抛出异常:

java.lang.IllegalStateException
at org.aspectj.weaver.ResolvedTypeMunger.<init>(ResolvedTypeMunger.java:69)
at org.aspectj.weaver.MethodDelegateTypeMunger.<init>(MethodDelegateTypeMunger.java:61)
at org.aspectj.weaver.bcel.AtAjAttributes.handleDeclareParentsAnnotation(AtAjAttributes.java:852)
at org.aspectj.weaver.bcel.AtAjAttributes.readAj5ClassAttributes(AtAjAttributes.java:384)
at org.aspectj.weaver.bcel.BcelObjectType.ensureAspectJAttrib ... ob.java:241)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:53)

Compile error: IllegalStateException thrown: Use generic type, not raw type

我的entityMongoController代码是:

public class EntityMongoController<T1> {
 ...
}

那么我怎样才能实现这个目标呢？或者还有其他选择吗？您必须记住，我正在使用 spring 配置文件，因此使用 native aspectj 不是替代方案。

Answer 1

让我们暂时假设，如果您按照 Spring 的文档了解如何将 native AspectJ 集成到您的 Spring 项目中，那么 native AspectJ 对您来说并不是一个阻碍。在这种情况下，您可以执行以下操作(我使用 native AspectJ 语法，因为从可读性/表达能力的角度来看，注释式 @AspectJ 语法有很多缺点):

与嵌入式方面的接口(interface)提供默认实现:

package de.scrum_master.app;

public interface IEntityController<T> {
    public void setEntity(T entity);
    public T getEntity();

    static aspect EntityControllerAspect {
        private T IEntityController.entity;
        public void IEntityController.setEntity(T entity) { this.entity = entity; }
        public T IEntityController.getEntity() { return entity; }

        declare parents : @EntityController * implements IEntityController;
    }
}

带有示例 main 方法的带注释的类，显示了效果:

package de.scrum_master.app;

import java.lang.reflect.Method;

@EntityController
public class MyAnnotatedController<T> {
    public void doSomething() {
        System.out.println("Doing something");
    }

    public static void main(String[] args) {
        // Use class type directly so as to call its method
        MyAnnotatedController<String> annotatedTextController = new MyAnnotatedController<>();
        annotatedTextController.doSomething();

        // Print all declared methods (should also show interface methods introduced via ITD)
        for (Method method : annotatedTextController.getClass().getDeclaredMethods()) {
            if (!method.getName().startsWith("ajc$"))
                System.out.println(method);
        }

        // Prove that class type is compatible with interface type
        IEntityController<String> entityTextController = annotatedTextController;
        entityTextController.setEntity("foo");
        // Would not work here because generic interface type is type-safe:
        // entityTextController.setEntity(123);
        System.out.println("Entity value = " + entityTextController.getEntity());

        // Create another object and directly assign it to interface type
        IEntityController<Integer> entityNumberController = new MyAnnotatedController<>();
        entityNumberController.setEntity(123);
        // Would not work here because generic interface type is type-safe:
        // entityNumberController.setEntity("foo");
        System.out.println("Entity value = " + entityNumberController.getEntity());
    }
}

控制台输出:

Doing something
public static void de.scrum_master.app.MyAnnotatedController.main(java.lang.String[])
public java.lang.Object de.scrum_master.app.MyAnnotatedController.getEntity()
public void de.scrum_master.app.MyAnnotatedController.setEntity(java.lang.Object)
public void de.scrum_master.app.MyAnnotatedController.doSomething()
Entity value = foo
Entity value = 123

如果您不理解我的代码片段，请随时提出进一步的问题。