Spring CGLIB代理仅拦截公共方法调用

Question

Spring文档说明：

@SpringBootApplication
public class DemoApplication implements CommandLineRunner {

@Autowired
private StudentService studentService;

public static void main(String[] args) {
    SpringApplication.run(DemoApplication.class, args);
}

@Bean
StudentService studentService() {
    ProxyFactory proxyFactory = new ProxyFactory(new StudentService());
    proxyFactory.setProxyTargetClass(true);
    proxyFactory.addAdvice(new MethodInterceptor() {
        @Override
        public Object invoke(MethodInvocation invocation) throws Throwable {
            System.out.println("method " + invocation.getMethod() + " is called on " +
                    invocation.getThis() + " with args " + invocation.getArguments());
            Object ret = invocation.proceed();
            System.out.println("method " + invocation.getMethod() + " returns " + ret);
            return ret;
        }
    });
    return (StudentService) proxyFactory.getProxy();
}

@Override
public void run(String... args) throws Exception {
    studentService.doIt();
}

class StudentService {

    void doIt() {
        System.out.println("doIt");
    }
}

输出：

method void com.example.demo.DemoApplication$StudentService.doIt() is called on com.example.demo.DemoApplication$StudentService@127a7a2e with args [Ljava.lang.Object;@14008db3
doIt
method void com.example.demo.DemoApplication$StudentService.doIt() returns null

同样-通过实验-CGLIB库（不使用spring，使用增强器类）也允许代理包级方法。

更新

@SpringBootApplication
public class DemoApplication implements CommandLineRunner {

    @Autowired
    private ExampleService exampleService;
    @Autowired
    private XExampleService xExampleService;
    @Autowired
    private XXExampleService xxExampleService;

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }

    @Override
    public void run(String... args) throws Exception {
        System.out.println(exampleService.getClass());
        System.out.println(xExampleService.getClass());
        System.out.println(xxExampleService.getClass());
    }


    @Service
    class ExampleService {

        void tranx() {

        }
    }

    @Service
    class XExampleService {

        @org.springframework.transaction.annotation.Transactional
        void tranx() {

        }
    }

    @Service
    class XXExampleService {

        @Transactional
        public void tranx() {

        }
    }
}

class com.example.demo.DemoApplication$ExampleService
class com.example.demo.DemoApplication$XExampleService
class com.example.demo.DemoApplication$XXExampleService$$EnhancerBySpringCGLIB$$2b1603e8

我想我找到了接受公共方法的这种行为只会发生的地方。它发生在AnnotationTransactionAttributeSource处，这是切入点(TransactionAttributeSourcePointcut)使用的。

来自代码：

/**
 * Create a custom AnnotationTransactionAttributeSource, supporting
 * public methods that carry the {@code Transactional} annotation
 * or the EJB3 {@link javax.ejb.TransactionAttribute} annotation.
 * @param publicMethodsOnly whether to support public methods that carry
 * the {@code Transactional} annotation only (typically for use
 * with proxy-based AOP), or protected/private methods as well
 * (typically used with AspectJ class weaving)
 */
public AnnotationTransactionAttributeSource(boolean publicMethodsOnly) {

Answer 1

可能的答案是，基于Java的代理不能使用package-private方法（因为Java实现类不能为接口实现的方法分配较弱的访问权限）。

所以这可能会阻止spring团队对包私有方法进行操作，即使CGLib可以代理它们。