使用@Before注解的Spring AOP AspectJ Before Advice示例

转x33g5p2x  于2022-10-16 转载在 Spring  
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在这个Spring AOP示例中，我们将学习在基于Spring的应用程序中使用AspectJ @Before注解。我们可以使用@Before注解在一个方面中声明before-advice。
用@Before注解的Before-advice方法将在连接点之前执行。除非抛出异常，否则这些方法不会阻止目标方法的执行。
在本例中，我们将创建一个简单的spring引导应用程序，添加日志方面，然后根据@Before注解中传递的切入点信息调用方面方法。

AspectJ@Before注解用法

以下代码段显示了@Before注解的用法：

  1. @Aspect
  2. @Component
  3. public class LoggingAspect {
  5.     private final Logger LOGGER = LoggerFactory.getLogger(this.getClass());
  7.     @Before("execution(* net.guides.springboot2.springaop.service.EmployeeService.*(..))")
  8.     public void logBeforeAllMethods(JoinPoint joinPoint) {
  9.         LOGGER.debug("****LoggingAspect.logBeforeAllMethods() : " + joinPoint.getSignature().getName());
  10.     }
  12.     @Before("execution(* net.guides.springboot2.springaop.service.EmployeeService.getEmployeeById(..))")
  13.     public void logBeforeGetEmployee(JoinPoint joinPoint) {
  14.         LOGGER.debug("****LoggingAspect.logBeforeGetEmployee() : " + joinPoint.getSignature().getName());
  15.     }
  17.     @Before("execution(* net.guides.springboot2.springaop.service.EmployeeService.createEmployee(..))")
  18.     public void logBeforeAddEmployee(JoinPoint joinPoint) {
  19.         LOGGER.debug("****LoggingAspect.logBeforeCreateEmployee() : " + joinPoint.getSignature().getName());
  20.     }
  21. }

让我们用一个完整的逐步示例演示@Before注解的用法。

Maven依赖项

  1. <?xmlversion="1.0"encoding="UTF-8"?>
  2. <project
  3.     xmlns="http://maven.apache.org/POM/4.0.0"
  4.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  5.  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  6.     <modelVersion>4.0.0</modelVersion>
  7.     <groupId>net.guides.springboot2</groupId>
  8.     <artifactId>springboot2-springaop-example</artifactId>
  9.     <version>0.0.1-SNAPSHOT</version>
  10.     <packaging>jar</packaging>
  11.     <name>springboot2-springaop-example</name>
  12.     <description>Demo project for Spring Boot</description>
  13.     <parent>
  14.         <groupId>org.springframework.boot</groupId>
  15.         <artifactId>spring-boot-starter-parent</artifactId>
  16.         <version>2.1.4.RELEASE</version>
  17.         <relativePath />
  18.         <!-- lookup parent from repository -->
  19.     </parent>
  20.     <properties>
  21.         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  22.         <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
  23.         <java.version>1.8</java.version>
  24.     </properties>
  25.     <dependencies>
  26.         <dependency>
  27.             <groupId>org.springframework.boot</groupId>
  28.             <artifactId>spring-boot-starter-aop</artifactId>
  29.         </dependency>
  30.     </dependencies>
  31.     <build>
  32.         <plugins>
  33.             <plugin>
  34.                 <groupId>org.springframework.boot</groupId>
  35.                 <artifactId>spring-boot-maven-plugin</artifactId>
  36.             </plugin>
  37.         </plugins>
  38.     </build>
  39. </project>

项目结构

以下项目结构供您参考-

创建特性-LogginAspect.java

让我们使用基于Java的配置创建LoggingAspect。下面是一个带AspectJ注解的类和方法，其中包含切入点信息：

  1. @Aspect
  2. @Component
  3. public class LoggingAspect {
  5.     private final Logger LOGGER = LoggerFactory.getLogger(this.getClass());
  7.     @Before("execution(* net.guides.springboot2.springaop.service.EmployeeService.*(..))")
  8.     public void logBeforeAllMethods(JoinPoint joinPoint) {
  9.         LOGGER.debug("****LoggingAspect.logBeforeAllMethods() : " + joinPoint.getSignature().getName());
  10.     }
  12.     @Before("execution(* net.guides.springboot2.springaop.service.EmployeeService.getEmployeeById(..))")
  13.     public void logBeforeGetEmployee(JoinPoint joinPoint) {
  14.         LOGGER.debug("****LoggingAspect.logBeforeGetEmployee() : " + joinPoint.getSignature().getName());
  15.     }
  17.     @Before("execution(* net.guides.springboot2.springaop.service.EmployeeService.createEmployee(..))")
  18.     public void logBeforeAddEmployee(JoinPoint joinPoint) {
  19.         LOGGER.debug("****LoggingAspect.logBeforeCreateEmployee() : " + joinPoint.getSignature().getName());
  20.     }
  21. }

创建Java POJO-Employee.Java

  1. package net.guides.springboot2.springaop.model;
  3. public class Employee {
  5.  private long id;
  6.  private String firstName;
  7.  private String lastName;
  8.  private String emailId;
  9.  
  10.  public Employee() {
  11.   
  12.  }
  13.  
  14.  public Employee(long id, String firstName, String lastName, String emailId) {
  15.   this.id = id;
  16.   this.firstName = firstName;
  17.   this.lastName = lastName;
  18.   this.emailId = emailId;
  19.  }
  20.  
  21.  public long getId() {
  22.   return id;
  23.  }
  24.  public void setId(long id) {
  25.   this.id = id;
  26.  }
  27.  
  28.  public String getFirstName() {
  29.   return firstName;
  30.  }
  31.  public void setFirstName(String firstName) {
  32.   this.firstName = firstName;
  33.  }
  34.  
  35.  public String getLastName() {
  36.   return lastName;
  37.  }
  38.  public void setLastName(String lastName) {
  39.   this.lastName = lastName;
  40.  }
  41.  
  42.  public String getEmailId() {
  43.   return emailId;
  44.  }
  45.  public void setEmailId(String emailId) {
  46.   this.emailId = emailId;
  47.  }
  49.  @Override
  50.  public String toString() {
  51.   return "Employee [id=" + id + ", firstName=" + firstName + ", lastName=" + lastName + ", emailId=" + emailId
  52.     + "]";
  53.  } 
  54. }

创建服务方法-EmployeeService.java

让我们为Employee创建几个需要执行的方面的服务方法。

  1. package net.guides.springboot2.springaop.service;
  3. import java.util.ArrayList;
  4. import java.util.List;
  6. import org.springframework.stereotype.Service;
  8. import net.guides.springboot2.springaop.model.Employee;
  10. /**
  11. * Employee Service
  12. * 
  13. * @author Ramesh
  14. *
  15. */
  16. @Service
  17. public class EmployeeService {
  19.     private List < Employee > employees = new ArrayList < > ();
  21.     public List < Employee > getAllEmployees() {
  22.         System.out.println("Method getAllEmployees() called");
  23.         return employees;
  24.     }
  26.     public Employee getEmployeeById(Long employeeId) {
  27.         System.out.println("Method getEmployeeById() called");
  28.         for (Employee employee: employees) {
  29.             if (employee.getId() == Long.valueOf(employeeId)) {
  30.                 return employee;
  31.             }
  32.         }
  33.         return null;
  34.     }
  36.     public void addEmployee(Employee employee) {
  37.         System.out.println("Method addEmployee() called");
  38.         employees.add(employee);
  39.     }
  41.     public void updateEmployee(Employee employeeDetails) {
  42.         System.out.println("Method updateEmployee() called");
  43.         for (Employee employee: employees) {
  44.             if (employee.getId() == Long.valueOf(employeeDetails.getId())) {
  45.                 employees.remove(employee);
  46.                 employees.add(employeeDetails);
  47.             }
  48.         }
  49.     }
  51.     public void deleteEmployee(Long employeeId) {
  52.         System.out.println("Method deleteEmployee() called");
  53.         for (Employee employee: employees) {
  54.             if (employee.getId() == Long.valueOf(employeeId)) {
  55.                 employees.remove(employee);
  56.             }
  57.         }
  58.     }
  59. }

测试Spring AspectJ配置和执行

现在，让我们使用Spring boot Application测试以上配置的方面是否在给定的切入点信息上执行：

  1. package net.guides.springboot2.springaop;
  3. import org.springframework.boot.SpringApplication;
  4. import org.springframework.boot.autoconfigure.SpringBootApplication;
  5. import org.springframework.context.ApplicationContext;
  7. import net.guides.springboot2.springaop.model.Employee;
  8. import net.guides.springboot2.springaop.service.EmployeeService;
  10. @SpringBootApplication
  11. public class Application {
  13.     public static void main(String[] args) {
  14.         ApplicationContext applicationContext = SpringApplication.run(Application.class, args);
  15.         EmployeeService employeeService = applicationContext.getBean(EmployeeService.class);
  16.         employeeService.addEmployee(new Employee(100 L, "ramesh", "fadatare", "ramesh@gmail.com"));
  17.         employeeService.getEmployeeById(100 L);
  18.         employeeService.getAllEmployees();
  19.     }
  20. }

输出：

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原文链接 : https://www.javaguides.net/2019/05/spring-aop-aspectj-before-advice-example-using-before-annotation.html

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