前后端分离的博客系统源码 Java

以下是一个简单的前后端分离的博客系统的 Java 代码示例，使用 Spring Boot 框架和 MySQL 数据库。

前端代码可以使用 Vue.js 或 React 等框架开发，这里不再给出示例。

### 后端代码

#### 实体类

@Entity
@Table(name = "articles")
public class Article {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String title;
    private String content;
    @Column(name = "created_at")
    private Date createdAt;
    @Column(name = "updated_at")
    private Date updatedAt;
    // 省略 getter 和 setter 方法
}

#### 数据访问层

@Repository
public interface ArticleRepository extends JpaRepository<Article, Long> {
}

#### 服务层

@Service
public class ArticleService {
    @Autowired
    private ArticleRepository articleRepository;

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

    public Article getArticleById(Long id) {
        return articleRepository.findById(id)
                .orElseThrow(() -> new ResourceNotFoundException("Article", "id", id));
    }

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

    public Article updateArticle(Long id, Article articleDetails) {
        Article article = getArticleById(id);
        article.setTitle(articleDetails.getTitle());
        article.setContent(articleDetails.getContent());
        article.setUpdatedAt(new Date());
        return articleRepository.save(article);
    }

    public void deleteArticle(Long id) {
        Article article = getArticleById(id);
        articleRepository.delete(article);
    }
}

#### 控制器层

@RestController
@RequestMapping("/api/articles")
public class ArticleController {
    @Autowired
    private ArticleService articleService;

    @GetMapping("")
    public List<Article> getAllArticles() {
        return articleService.getAllArticles();
    }

    @GetMapping("/{id}")
    public Article getArticleById(@PathVariable(value = "id") Long id) {
        return articleService.getArticleById(id);
    }

    @PostMapping("")
    public Article createArticle(@Valid @RequestBody Article article) {
        return articleService.createArticle(article);
    }

    @PutMapping("/{id}")
    public Article updateArticle(@PathVariable(value = "id") Long id,
                                  @Valid @RequestBody Article articleDetails) {
        return articleService.updateArticle(id, articleDetails);
    }

    @DeleteMapping("/{id}")
    public ResponseEntity<?> deleteArticle(@PathVariable(value = "id") Long id) {
        articleService.deleteArticle(id);
        return ResponseEntity.ok().build();
    }
}

#### 异常处理

@ControllerAdvice
public class GlobalExceptionHandler {
    @ExceptionHandler(ResourceNotFoundException.class)
    public ResponseEntity<?> resourceNotFoundException(ResourceNotFoundException ex) {
        ErrorResponse errorResponse = new ErrorResponse(HttpStatus.NOT_FOUND.value(), ex.getMessage());
        return new ResponseEntity<>(errorResponse, HttpStatus.NOT_FOUND);
    }

    @ExceptionHandler(MethodArgumentNotValidException.class)
    public ResponseEntity<?> validationException(MethodArgumentNotValidException ex) {
        ErrorResponse errorResponse = new ErrorResponse(HttpStatus.BAD_REQUEST.value(), "Validation failed");
        List<String> errors = ex.getBindingResult().getFieldErrors().stream()
                .map(error -> error.getField() + ": " + error.getDefaultMessage())
                .collect(Collectors.toList());
        errorResponse.setErrors(errors);
        return new ResponseEntity<>(errorResponse, HttpStatus.BAD_REQUEST);
    }

    @ExceptionHandler(Exception.class)
    public ResponseEntity<?> defaultExceptionHandler(Exception ex) {
        ErrorResponse errorResponse = new ErrorResponse(HttpStatus.INTERNAL_SERVER_ERROR.value(), "Internal server error");
        return new ResponseEntity<>(errorResponse, HttpStatus.INTERNAL_SERVER_ERROR);
    }
}

#### 异常类

public class ResourceNotFoundException extends RuntimeException {
    private String resourceName;
    private String fieldName;
    private Object fieldValue;

    public ResourceNotFoundException(String resourceName, String fieldName, Object fieldValue) {
        super(String.format("%s not found with %s : '%s'", resourceName, fieldName, fieldValue));
        this.resourceName = resourceName;
        this.fieldName = fieldName;
        this.fieldValue = fieldValue;
    }

    public String getResourceName() {
        return resourceName;
    }

    public String getFieldName() {
        return fieldName;
    }

    public Object getFieldValue() {
        return fieldValue;
    }
}

#### 错误响应类

public class ErrorResponse {
    private int status;
    private String message;
    private List<String> errors;

    public ErrorResponse(int status, String message) {
        this.status = status;
        this.message = message;
    }

    public int getStatus() {
        return status;
    }

    public void setStatus(int status) {
        this.status = status;
    }

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }

    public List<String> getErrors() {
        return errors;
    }

    public void setErrors(List<String> errors) {
        this.errors = errors;
    }
}

### 配置文件

#### application.properties

spring.datasource.url=jdbc:mysql://localhost:3306/blog?useSSL=false&characterEncoding=utf8&serverTimezone=GMT%2B8
spring.datasource.username=root
spring.datasource.password=root
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

spring.jpa.hibernate.ddl-auto=update
spring.jpa.show-sql=true
spring.jpa.properties.hibernate.format_sql=true

### 总结

以上是一个简单的前后端分离的博客系统的 Java 代码示例，该示例使用了 Spring Boot 框架、MySQL 数据库和 JPA 数据访问层。该示例中，实体类、数据访问层、服务层和控制器层分别处理了数据的持久化、业务逻辑和 RESTful API 接口的实现，并使用了全局异常处理来处理异常情况。