【10】Spring Boot系列之通用 mapper 改进AOP

Love The Way You Lie 2022-03-27 05:14 284阅读 0赞

在 [【9】Spring Boot系列之通用 mapper][9_Spring Boot_ mapper] 基础上作以下改进：  
（1）定义注解：

@Documented
    @Retention(RetentionPolicy.RUNTIME)
    @Target(ElementType.METHOD)
    public @interface PagingQuery { 
        String pageNumParam() default "pageNum";//页号的参数名
        String pageSizeParam() default "pageSize";//每页行数的参数名
    }

（2）定义切面

@Aspect
    @Component
    public class PagingAop { 
    	@Around("@annotation(pagingQuery)")
    	public Object pagingQuery(ProceedingJoinPoint joinPoint, PagingQuery pagingQuery) throws Throwable { 
    		
    		MethodSignature signature = (MethodSignature) joinPoint.getSignature();
    		Class<?> returnType = signature.getMethod().getReturnType(); //返回类型
    		
    		/** * 返回类型returnType 必须为 Object，不能为List; * 否则报错：com.github.pagehelper.PageInfo cannot be cast to java.util.List * 当（3）中的 findAllUser 返回方法为 List<UserModel> 时，不会执行分页操作 */
    		if(returnType == Object.class){  
    			String pageNumParam = pagingQuery.pageNumParam();
    			String pageSizeParam = pagingQuery.pageSizeParam();
    			
    			//获取request，从中获取分页参数
    			ServletRequestAttributes currentRequestAttributes = 
    					(ServletRequestAttributes) RequestContextHolder.currentRequestAttributes();
    			HttpServletRequest request = currentRequestAttributes.getRequest();
    			String pageNum = request.getParameter(pageNumParam);
    			String pageSize = request.getParameter(pageSizeParam);
    			if (StringUtils.isNotBlank(pageNum) && StringUtils.isNotBlank(pageSize) ) { 
    				try { 
    					PageHelper.startPage(Integer.valueOf(pageNum), Integer.valueOf(pageSize));
    					Object result = joinPoint.proceed();
    					// 建议自己实现返回类型，官方自带的返回数据太冗余了
    					return new PageInfo<>((List<?>) result);
    				} finally { // 保证线程变量被清除
    					if (PageHelper.getLocalPage() != null){ 
    						PageHelper.clearPage();
    					}
    				}
    			}
    		}
    		return joinPoint.proceed();
    	}
    }

（3）Controller 使用：

//PagingQuery:当前端调用时传的参数名跟默认不一致时需指定参数名
    @PagingQuery(pageNumParam = "page", pageSizeParam = "size") 
    @GetMapping("/all")
    @ResponseBody
    public Object findAllUser() { 
    	List<UserModel> list = userService.findAllUser();
    	return list;
    }

参考：  
[https://www.jianshu.com/p/61334f4a45d2][https_www.jianshu.com_p_61334f4a45d2]  
[https://www.2cto.com/kf/201801/716420.html][https_www.2cto.com_kf_201801_716420.html]

[9_Spring Boot_ mapper]: https://blog.csdn.net/lishk314/article/details/86303601
[https_www.jianshu.com_p_61334f4a45d2]: https://www.jianshu.com/p/61334f4a45d2
[https_www.2cto.com_kf_201801_716420.html]: https://www.2cto.com/kf/201801/716420.html