To enable Aspect-Oriented Programming in Spring Boot, first add the required dependency to your pom.xml:

<dependency>
    <groupId>org.aspectj</groupId>
    <artifactId>aspectjweaver</artifactId>
    <version>1.9.1</version>
</dependency>

Here's the complete implementation with all necessary components:

1. JournalEntry.java (Domain Object)

package com.example.aopdemo;

public class JournalEntry {
    private String date;
    private String tags;
    private String content;
    private String heading;

    // Getters and Setters
    public String getHeading() { return heading; }
    public void setHeading(String heading) { this.heading = heading; }
    public String getDate() { return date; }
    public void setDate(String date) { this.date = date; }
    public String getTags() { return tags; }
    public void setTags(String tags) { this.tags = tags; }
    public String getContent() { return content; }
    public void setContent(String content) { this.content = content; }
}

2. JournalService.java (Service Interface)

package com.example.aopdemo;

public interface JournalService {
    void createEntry(JournalEntry entry);
    void displayEntry(JournalEntry entry) throws Exception;
}

3. JournalServiceImpl.java (Service Implemantation)

package com.example.aopdemo;

import org.springframework.stereotype.Service;

@Service
public class JournalServiceImpl implements JournalService {

    @Override
    public void createEntry(JournalEntry entry) {
        System.out.println(entry.getHeading());
    }

    @Override
    public void displayEntry(JournalEntry entry) throws Exception {
        System.out.println("Heading: " + entry.getHeading());
        System.out.println("Date: " + entry.getDate());
        System.out.println("Tags: " + entry.getTags());
        System.out.println("Content: " + entry.getContent());
        throw new Exception("Test exception");
    }
}

4. JournalAspect.java (AOP Configuration)

package com.example.aopdemo;

import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.*;
import org.springframework.stereotype.Component;

@Component
@Aspect
public class JournalAspect {

    @Pointcut("execution(* com.example.aopdemo.JournalServiceImpl.displayEntry(..))")
    public void displayPointcut() {}
    
    @Before("displayPointcut() && args(entry)")
    public void beforeDisplay(JoinPoint jp, JournalEntry entry) {
        System.out.println("AOP - Method Args: " + jp.getArgs()[0].getClass());
        System.out.println("AOP - Target Class: " + jp.getTarget().getClass());
    }
    
    @After("displayPointcut()")
    public void afterDisplay() {
        System.out.println("AOP - After method execution");
    }
    
    @AfterReturning("displayPointcut()")
    public void afterSuccessfulDisplay() {
        System.out.println("AOP - After successful execution");
    }
    
    @AfterThrowing("displayPointcut()")
    public void afterFailedDisplay() {
        System.out.println("AOP - After exception thrown");
    }
}

5. JournalController.java (REST Controller)

package com.example.aopdemo;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

@RestController
@RequestMapping("/api/journal")
public class JournalController {
    
    @Autowired
    private JournalService journalService;
    
    @PostMapping("/display")
    public JournalEntry displayEntry() throws Exception {
        JournalEntry entry = new JournalEntry();
        entry.setHeading("Building Dreams");
        entry.setDate("2023-12-31");
        entry.setTags("ambition,technology,future");
        entry.setContent("Creating something meaningful...");
        journalService.displayEntry(entry);
        return entry;
    }
}

6. MainApplication.java (Spring Boot Starter)

package com.example.aopdemo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.support.SpringBootServletInitializer;
import org.springframework.context.annotation.Bean;

@SpringBootApplication
public class MainApplication extends SpringBootServletInitializer {
    
    public static void main(String[] args) {
        SpringApplication.run(MainApplication.class, args);
    }
    
    @Bean
    public JournalAspect journalAspect() {
        return new JournalAspect();
    }
}

AOP provides powerful capabilities for cross-cutting concerns like logging and transaction management. The aspect configuration allows intercepting method executions at specific join points with various advice types.