【Spring Boot】四种核心类的依赖关系：实体类、数据处理类、业务处理类、控制器类-Toy模板网

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//1.配置项目环境，创建Spring Boot项目。
//2.数据库设置，配置数据库。
//3.创建实体类，映射到数据库。
//4.创建数据处理层类，Repository
//5.创建业务处理类，Service类
//6.创建控制器类，Controller类

Article.java

java
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

@Entity
   public class Article{
@Id
       @GeneratedValue(strategy = GenerationType.AOTU)
       private Long id;
   private String title;
   private String content;
   private String author;

//省略构造函数、getter和setter方法
//省略toString方法
//一个实体类完成了！
}

ArticleRepository.java（数据访问层类）
   '''java
   import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Query;
import java.util.List;
public interface ArticleRepository extends JpaRepository<Article,Long>{
//可以在此自定义查询方法
//根据作者名查询文章
List<Article> findByAuthor(String author);
//根据标题和作者查询文章
List<Article> findByTitleAndAuthor(String title,String author);
//使用JPQL查询语句查询文章
@Query("Select a FROM Article a WHERE a.title LIKE %:keyword% OR a.content LIKE %:keyword%")
List<Article> fintByKeyword(String keyword);
}

ArticleService.Java(业务逻辑层)：
   '''java
   import org.springframework.beans.factory. annotation.Autowired;
import org.springframework.stereotype.Service;
import java.util.List;
import java.util.Optional;

@Service
   public class ArticleService{
private final ArticleRepository articleRepository;

   @Autowired
   public ArticleService(ArticleRepository articleRepository){
   this.articleRepository = articleRepository;
   }

   public List<Article>getAllArticles(){
   return articleRepository.findAll();
   }

public Optional<Article>getArticleById(Long id){
       return articleRepository.findByID(id);
   }

   public Article createArticle(Article article){
   return articleRepository.save(article);
   }

   /**
   public void updateArticle(Long id, Article article) {
Optional<Article> existingArticle = articleRepository.findById(id);
if (existingArticle.isPresent()) {
Article updatedArticle = existingArticle.get();
updatedArticle.setTitle(article.getTitle());
updatedArticle.setContent(article.getContent());
updatedArticle.setAuthor(article.getAuthor());
articleRepository.save(updatedArticle);
}
}

   **/

   public void deleteArticle(Long id){
   articleRepository.deleteById(id);
   }

}

ArticleController.java(控制器类)：
   '''java
   import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;

import java.util.List;
import java.util.Optional;

@RestContrller
@RequestMapping("/articles")
public class ArticleController{
private final ArticleService articleService;

   @Autowired
   public ArticleControler(
   ArticleService articleService
   ){
   tihs.articleService = articleService;
   }

   @GetMapping
       public ResponseEntity<List<Article>>getAllArticles(){
   List<Article>articles = articleService.getAllArticles;
   return new ResponseEntity<>(articles,HttpStatus.OK)
   }
//以下为粘贴
   @GetMapping("/{id}")
public ResponseEntity<Article> getArticleById(@PathVariable Long id) {
Optional<Article> article = articleService.getArticleById(id);
return article.map(value -> new ResponseEntity<>(value, HttpStatus.OK))
.orElseGet(() -> new ResponseEntity<>(HttpStatus.NOT_FOUND));
}

@PostMapping
public ResponseEntity<Article> createArticle(@RequestBody Article article) {
Article createdArticle = articleService.createArticle(article);
return new ResponseEntity<>(createdArticle, HttpStatus.CREATED);
}

@PutMapping("/{id}")
public ResponseEntity<Void> updateArticle(@PathVariable Long id, @RequestBody Article article) {
articleService.updateArticle(id, article);
return new ResponseEntity<>(HttpStatus.NO_CONTENT);
}

@DeleteMapping("/{id}")
public ResponseEntity<Void> deleteArticle(@PathVariable Long id) {
articleService.deleteArticle(id);
return new ResponseEntity<>(HttpStatus.NO_CONTENT);
}
}

}