Spring AOP AspectJ @Before Annotation Example

In this Spring AOP example, we will learn to use AspectJ @Before annotation in Spring-based applications. We can declare before advice in an aspect by using the @Before annotation.

Before advice methods annotated with @Before that will execute before the join point. These methods do not prevent the execution of the target method unless they throw an exception.

In this example, We will create a simple spring boot application, add logging aspect and then invoke aspect methods based on pointcuts information passed in a @Before annotation.

AspectJ @Before Annotation Usage

Below snippet shows usage of @Before annotation:

@Aspect
@Component
public class LoggingAspect {

    private final Logger LOGGER = LoggerFactory.getLogger(this.getClass());

    @Before("execution(* net.guides.springboot2.springaop.service.EmployeeService.*(..))")
    public void logBeforeAllMethods(JoinPoint joinPoint) {
        LOGGER.debug("****LoggingAspect.logBeforeAllMethods() : " + joinPoint.getSignature().getName());
    }

    @Before("execution(* net.guides.springboot2.springaop.service.EmployeeService.getEmployeeById(..))")
    public void logBeforeGetEmployee(JoinPoint joinPoint) {
        LOGGER.debug("****LoggingAspect.logBeforeGetEmployee() : " + joinPoint.getSignature().getName());
    }

    @Before("execution(* net.guides.springboot2.springaop.service.EmployeeService.createEmployee(..))")
    public void logBeforeAddEmployee(JoinPoint joinPoint) {
        LOGGER.debug("****LoggingAspect.logBeforeCreateEmployee() : " + joinPoint.getSignature().getName());
    }
}

Let's demonstrate the usage of @Before annotation with a complete step by step example.

Create a Maven Project

Use below articles to quickly creating maven based Java projects.

Maven Dependencies

<?xml version="1.0" encoding="UTF-8"?>
<project
    xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>net.guides.springboot2</groupId>
    <artifactId>springboot2-springaop-example</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>
    <name>springboot2-springaop-example</name>
    <description>Demo project for Spring Boot</description>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.4.RELEASE</version>
        <relativePath />
        <!-- lookup parent from repository -->
    </parent>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-aop</artifactId>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

Project Structure

Below project structure for your reference -

diagram here

Create Aspect - LogginAspect.java

Let's create a LoggingAspect using Java-based configuration. Here is an Aspectj annotated class and methods with pointcut information:

@Aspect
@Component
public class LoggingAspect {

    private final Logger LOGGER = LoggerFactory.getLogger(this.getClass());

    @Before("execution(* net.guides.springboot2.springaop.service.EmployeeService.*(..))")
    public void logBeforeAllMethods(JoinPoint joinPoint) {
        LOGGER.debug("****LoggingAspect.logBeforeAllMethods() : " + joinPoint.getSignature().getName());
    }

    @Before("execution(* net.guides.springboot2.springaop.service.EmployeeService.getEmployeeById(..))")
    public void logBeforeGetEmployee(JoinPoint joinPoint) {
        LOGGER.debug("****LoggingAspect.logBeforeGetEmployee() : " + joinPoint.getSignature().getName());
    }

    @Before("execution(* net.guides.springboot2.springaop.service.EmployeeService.createEmployee(..))")
    public void logBeforeAddEmployee(JoinPoint joinPoint) {
        LOGGER.debug("****LoggingAspect.logBeforeCreateEmployee() : " + joinPoint.getSignature().getName());
    }
}

Create a Java POJO - Employee.java

package net.guides.springboot2.springaop.model;

public class Employee {

	private long id;
	private String firstName;
	private String lastName;
	private String emailId;
	
	public Employee() {
		
	}
	
	public Employee(long id, String firstName, String lastName, String emailId) {
		this.id = id;
		this.firstName = firstName;
		this.lastName = lastName;
		this.emailId = emailId;
	}
	
	public long getId() {
		return id;
	}
	public void setId(long id) {
		this.id = id;
	}
	
	public String getFirstName() {
		return firstName;
	}
	public void setFirstName(String firstName) {
		this.firstName = firstName;
	}
	
	public String getLastName() {
		return lastName;
	}
	public void setLastName(String lastName) {
		this.lastName = lastName;
	}
	
	public String getEmailId() {
		return emailId;
	}
	public void setEmailId(String emailId) {
		this.emailId = emailId;
	}

	@Override
	public String toString() {
		return "Employee [id=" + id + ", firstName=" + firstName + ", lastName=" + lastName + ", emailId=" + emailId
				+ "]";
	}	
}

Create service methods - EmployeeService.java

Let's create a few service methods for Employee on which aspects need to be executed.

package net.guides.springboot2.springaop.service;

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

import org.springframework.stereotype.Service;

import net.guides.springboot2.springaop.model.Employee;

/**
 * Employee Service
 * 
 * @author Ramesh
 *
 */
@Service
public class EmployeeService {

    private List < Employee > employees = new ArrayList < > ();

    public List < Employee > getAllEmployees() {
        System.out.println("Method getAllEmployees() called");
        return employees;
    }

    public Employee getEmployeeById(Long employeeId) {
        System.out.println("Method getEmployeeById() called");
        for (Employee employee: employees) {
            if (employee.getId() == Long.valueOf(employeeId)) {
                return employee;
            }
        }
        return null;
    }

    public void addEmployee(Employee employee) {
        System.out.println("Method addEmployee() called");
        employees.add(employee);
    }

    public void updateEmployee(Employee employeeDetails) {
        System.out.println("Method updateEmployee() called");
        for (Employee employee: employees) {
            if (employee.getId() == Long.valueOf(employeeDetails.getId())) {
                employees.remove(employee);
                employees.add(employeeDetails);
            }
        }
    }

    public void deleteEmployee(Long employeeId) {
        System.out.println("Method deleteEmployee() called");
        for (Employee employee: employees) {
            if (employee.getId() == Long.valueOf(employeeId)) {
                employees.remove(employee);
            }
        }
    }
}

Test Spring AspectJ Configuration and Execution

Now let’s test whether above configured aspects execute on given pointcut information using Spring boot Application:

package net.guides.springboot2.springaop;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContext;

import net.guides.springboot2.springaop.model.Employee;
import net.guides.springboot2.springaop.service.EmployeeService;

@SpringBootApplication
public class Application {

    public static void main(String[] args) {
        ApplicationContext applicationContext = SpringApplication.run(Application.class, args);
        EmployeeService employeeService = applicationContext.getBean(EmployeeService.class);
        employeeService.addEmployee(new Employee(100 L, "ramesh", "fadatare", "ramesh@gmail.com"));
        employeeService.getEmployeeById(100 L);
        employeeService.getAllEmployees();
    }
}

Output:

diagram here