当一个对象的方法调用在列表中可用时，Spring AOP pointcut不会被触发。

问题描述 投票：0回答：1

我有一个spring boot应用，有如下几个类，配置类和方面。下面的例子是为了说明我所面临的问题。

我有一个office类，它的打印机列表是使用外部属性文件配置创建的依赖关系，我想在调用打印机.getFilename方法时执行一个方面。我想在调用Printer.getFilename方法时执行一个方面。如果我有打印机列表，就不会触发方面，但是当我有一个没有列表的打印机对象时，它就会工作。

package com.example

public class Office {
   private final List<Printer> printersList;

   public Office(Printer printersList){
     this.printersList = printersList;
   }

   public void printFiles(){
      for(Printer printer: printersList)
        printer.getFileName();
   }
}

package com.example

public class Printer {
  private deviceId;

  public String getFileName(){
     return "fileName";
  }
}

@Configuration
public class ApplicationConfiguration{
  @Bean
  public Office office(){
    List<Printer> printerList = new ArrayList<>();
    // Adding to the list based on printer id based on some external property file configuration
    printerList.add(new Printer());
    printerList.add(new Printer());
    return new Office(printerList);
  }
}

@Aspect
@Component
public class PrinterFileNameAspect {
    @Pointcut("execution(* com.example.Printer.getFileName())")
    private void getFileNameJp() {}

    @Around("getFileNameJp()")
    public String returnFileName(ProceedingJoinPoint pjp) {
        return "Modified File Name";
    }
}

我发现Bean的列表没有在Spring容器中注册。因此，我修改了配置类来注册Bean。

@Configuration
public class ApplicationConfiguration{
  @Autowired
  private GenericWebApplicationContext context;

  @Bean
  public Office office(){
    List<Printer> printerList = new ArrayList<>();
    // Adding to the list based on printer id
    Printer colorPrinter = new Printer();
    context.registerBean("colorPrinter", Printer.class, () -> colorPrinter);
    printerList.add(colorPrinter);
    Printer specialPrinter = new Printer();
    context.registerBean("specialPrinter", Printer.class, () -> specialPrinter);
    printerList.add(specialPrinter);
    return new Office(printerList);
  }
}

以上配置的改变并没有帮助。我想我错过了一些spring aop的基础知识。我想用Printer的列表来实现spring aop，因为我不能改变列表生成逻辑（列表生成逻辑很复杂，必须是动态的）。

java spring spring-boot spring-aop spring5
1个回答
2
投票

我添加了一个备选答案，因为你似乎很想学习如何使用新方法。GenericApplicationContext.registerBean(..) 在Spring 5中引入的。由于我不是Spring用户，我也想了解一下这是怎么回事，于是想到了这个解决方案。

同样，我提供的是完整的类定义。它们与我的第一个答案相似，但略有不同。具体来说。Printer 不再是一个原型范围的 @Component 但是一个POJO。我还是离开了 Office 为方便起见，将其改为单人组件。如果你也需要多个实例，你可以随时根据你的需要调整代码。

现在重要的是解决你的问题。在以编程方式注册Bean之后，你应该通过以下方式从应用程序上下文中获取它们 getBean() 而不仅仅是将手动创建的POJO实例添加到你的打印机列表中。只有当你从应用上下文中获取bean时，Spring才会在必要的地方照顾到也创建AOP代理。

package de.scrum_master.spring.q61661740;

public class Printer {
  private String deviceId;

  public Printer(String deviceId) {
    this.deviceId = deviceId;
  }

  public String getFileName() {
    return deviceId + ".pdf";
  }
}

package de.scrum_master.spring.q61661740;

import org.springframework.stereotype.Component;

import java.util.ArrayList;
import java.util.List;

@Component
public class Office {
  private final List<Printer> printersList = new ArrayList<>();

  public void addPrinter(Printer printer) {
    printersList.add(printer);
  }

  public void printFiles() {
    for (Printer printer : printersList)
      System.out.println(printer.getFileName());
  }
}

package de.scrum_master.spring.q61661740;

import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Pointcut;
import org.springframework.stereotype.Component;

@Aspect
@Component
public class PrinterFileNameAspect {
  // Package name is optional if aspect is in same name as Printer
  @Pointcut("execution(* de.scrum_master.spring.q61661740.Printer.getFileName())")
  private void getFileNameJp() {}

  @Around("getFileNameJp()")
  public String returnFileName(ProceedingJoinPoint pjp) throws Throwable {
    return "modified_" + pjp.proceed();
  }
}

package de.scrum_master.spring.q61661740;

import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.EnableAspectJAutoProxy;

import java.util.stream.Stream;

@SpringBootApplication
@Configuration
@EnableAspectJAutoProxy
public class Application {
  public static void main(String[] args) {
    try (AnnotationConfigApplicationContext appContext = new AnnotationConfigApplicationContext(Application.class)) {
      // If you want to get rid of the `@SpringBootApplication` annotation, add this:
      // appContext.scan(Application.class.getPackage().getName());
      Office office = appContext.getBean(Office.class);
      Stream
        .of("colorPrinter", "specialPrinter")
        .forEach(deviceID -> {
          appContext.registerBean(deviceID, Printer.class, () -> new Printer(deviceID));
          office.addPrinter(appContext.getBean(deviceID, Printer.class));
        });
      office.printFiles();
    }
  }
}

控制台日志看起来是这样的（缩短了）。

(...)
18:20:54.169 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'office'
18:20:54.177 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'colorPrinter'
18:20:54.178 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'specialPrinter'
colorPrinter.pdf
specialPrinter.pdf
(...)
1
投票

怎么样添加包含以下内容的包 Printer 类到SpringBoot应用类中，并在 @SpringBootApplication

@Aspect
@Component
public class PrinterAspect
{
    @Around( "getFileNameJp()" )
    private String returnFileName( ProceedingJoinPoint joinPoint ) throws Throwable
    {
        return "Modified File Name"; // This will always return this name
    }
}

最后，使启用 AspectJAutoproxy 用于申请

@SpringBootApplication(scanBasePackages = "com.example.*" )
@EnableAspectJAutoProxy( proxyTargetClass = true )
public class Application
{
    public static void main( String[] args )
    {
        SpringApplication.run( Application.class, args );
    }
}

你也错过了 @Component 在 Printer 和 Office 类。所以总的来说，你的 Office 类应该是这样的。

@Component
public class Office
{
    private final List<Printer> printer;

    public Office( List<Printer> printer )
    {
        this.printer = printer;
    }
    public void printFiles()
    {
        // my code logic ...
        // Demo logic
        for( Printer printer1 : printer )
        {
            System.out.println( printer1.getFileName() );
        }
        // my code logic ...
    }
}

而打印机类应该是这样的

@Component
public class Printer
{
    private int deviceId;
    private String fileName;

    public String getFileName()
    {
        // my code logic here ...
        fileName = String.valueOf( System.nanoTime() ); // demo logic
        return fileName;
    }
}

而用法应该是这样的。

@Autowired
private Office office;

@GetMapping( "/demo" )
public List<String> demo()
{
    office.printFiles();
    return fileNames(); // To be implemented
}
1
投票

这个基于原型scoped beans的简单解决方案怎么样？

package de.scrum_master.spring.q61661740;

import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Component;

@Component
@Scope("prototype")
public class Printer {
  public String getFileName() {
    return "fileName";
  }

  public void configureIndividually(String whatever) {
    System.out.println("printer being configured individually: " + whatever);
  }
}

package de.scrum_master.spring.q61661740;

import org.springframework.stereotype.Component;

import java.util.ArrayList;
import java.util.List;

@Component
public class Office {
  private final List<Printer> printersList = new ArrayList<>();

  public void addPrinter(Printer printer) {
    printersList.add(printer);
  }

  public void printFiles() {
    for (Printer printer : printersList)
      System.out.println(printer.getFileName());
  }
}

package de.scrum_master.spring.q61661740;

import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Pointcut;
import org.springframework.stereotype.Component;

@Aspect
@Component
public class PrinterFileNameAspect {
  // Package name is optional if aspect is in same name as Printer
  @Pointcut("execution(* de.scrum_master.spring.q61661740.Printer.getFileName())")
  private void getFileNameJp() {}

  @Around("getFileNameJp()")
  public String returnFileName(ProceedingJoinPoint pjp) {
    return "modified file name";
  }
}

package de.scrum_master.spring.q61661740;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.EnableAspectJAutoProxy;

@SpringBootApplication
@Configuration
@EnableAspectJAutoProxy(proxyTargetClass = true)
public class Application {
  public static void main(String[] args) {
    try (ConfigurableApplicationContext appContext = SpringApplication.run(Application.class, args)) {
      doStuff(appContext);
    }
  }

  private static void doStuff(ConfigurableApplicationContext appContext) {
    Printer colorPrinter = appContext.getBean(Printer.class);
    colorPrinter.configureIndividually("my color config");
    Printer specialPrinter = appContext.getBean(Printer.class);
    specialPrinter.configureIndividually("my special config");

    Office office = appContext.getBean(Office.class);
    office.addPrinter(colorPrinter);
    office.addPrinter(specialPrinter);
    office.printFiles();
  }
}

现在你可以让容器负责生成bean实例，但你仍然可以单独配置它们。我不明白为什么在这种情况下你必须手动注册bean。

控制台的日志会是

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.1.8.RELEASE)

2020-05-10 15:52:24.817  INFO 10404 --- [           main] d.s.spring.q61661740.Application         : Starting Application on Xander-Ultrabook with PID 10404 (C:\Users\alexa\Documents\java-src\spring-aop-playground\target\classes started by alexa in C:\Users\alexa\Documents\java-src\spring-aop-playground)
2020-05-10 15:52:24.821  INFO 10404 --- [           main] d.s.spring.q61661740.Application         : No active profile set, falling back to default profiles: default
2020-05-10 15:52:25.895  INFO 10404 --- [           main] .s.d.r.c.RepositoryConfigurationDelegate : Bootstrapping Spring Data repositories in DEFAULT mode.
2020-05-10 15:52:25.918  INFO 10404 --- [           main] .s.d.r.c.RepositoryConfigurationDelegate : Finished Spring Data repository scanning in 17ms. Found 0 repository interfaces.
2020-05-10 15:52:26.454  INFO 10404 --- [           main] trationDelegate$BeanPostProcessorChecker : Bean 'org.springframework.transaction.annotation.ProxyTransactionManagementConfiguration' of type [org.springframework.transaction.annotation.ProxyTransactionManagementConfiguration$$EnhancerBySpringCGLIB$$377fd151] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2020-05-10 15:52:27.148  INFO 10404 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2020-05-10 15:52:27.189  INFO 10404 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2020-05-10 15:52:27.190  INFO 10404 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.24]
2020-05-10 15:52:27.375  INFO 10404 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2020-05-10 15:52:27.376  INFO 10404 --- [           main] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 2486 ms
2020-05-10 15:52:27.681  INFO 10404 --- [           main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'applicationTaskExecutor'
2020-05-10 15:52:28.005  INFO 10404 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2020-05-10 15:52:28.007  INFO 10404 --- [           main] d.s.spring.q61661740.Application         : Started Application in 3.735 seconds (JVM running for 5.395)
printer being configured individually: my color config
printer being configured individually: my special config
modified file name
modified file name
2020-05-10 15:52:28.135  INFO 10404 --- [           main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Shutting down ExecutorService 'applicationTaskExecutor'
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