Spring CGLIB 代理仅拦截 public 方法调用

Question

Spring 文档指出：

CGLIB proxies intercept only public method calls! Do not call non-public methods on such a proxy. They are not delegated to the actual scoped target object.

https://docs.spring.io/spring/docs/current/spring-framework-reference/core.html#beans-factory-scopes-other

但经过观察，我认为要么我的实验（下面的代码）不好，要么这种行为随着时间的推移而改变了。

我观察到只有 final 或私有方法被绕过。

这是实验：(spring 版本：5.1.3)

@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

此外 - 通过实验 - CGLIB 库（没有 spring，使用增强器 class）也允许代理包级方法。

更新

我还有一个观察结果（与上面的相反）。在典型的 jdbc 应用程序中：

@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() {

        }
    }
}

输出：

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

这意味着，如果 spring 按照我的行为创建代理 - 就像在 TransactionInterceptor 中一样 - CGLIB 代理仅为 public 方法创建。

更新2

我想我发现了这种接受 public 方法的行为只发生在哪里。它发生在 PointCut (TransactionAttributeSourcePointcut) 使用的 AnnotationTransactionAttributeSource。

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

可能的答案是因为基于 Java 的代理无法使用 package-private 方法（因为 Java 实现类无法将较弱的访问权限分配给接口实现的方法） .

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。

Spring CGLIB 代理仅拦截 public 方法调用

Spring CGLIB proxies intercept only public method calls

java

spring

cglib