用模板模式优雅写出controller

朱雀 2020-10-07 15:13 835阅读 0赞

看一下你们的项目中是怎样写controller的呢，是不是看起来乱乱的不清晰，下面我们用模板模式来改造一下。

### 基类HttpCallback ###

public abstract class HttpCallback {
    
        protected abstract void checkParameter();
    
        protected abstract Result execute();
    
    }

### 模板类HttpTemplate ###

模板大致分为几个部分：

1、初始化上下文：因为这些数据可能在其他地方有用到，像userId呀，clientIp呀等。

2、打印请求日志，可以打印一些 请求方法，请求参数等信息，可以自行扩展

3、入参检查，如果说是对外暴露的接口，入参里有很多重复的字段，比如入参里有header、body，header里大致字段相同，就可以在这里进行统一的入参判断；像body里不同接口有不同的字段，那就在controller层每个方法里对body里的字段进行校验。

4、具体业务执行

5、组装结果（对于一些复杂的业务场景，一般分为业务结果bizResult和对外结果Result，service层查询出来的是bizResult，然后再组装成Result返回出去，这里先不做这个处理，如果有感兴趣的可以私信我）

6、处理业务异常和系统异常

7、打印耗时日志、业务日志等，清除线程变量

@Slf4j
    @Component
    public class HttpTemplate {
    
        /**
         * 日志 逗号 分隔
         */
        private static final String COMMA = ",";
    
        /**
         * 日志中为null时的替代符
         */
        private static final String NULL_REPLACE = "-";
    
        public Result execute(HttpServletRequest request, Class<? extends Result> resultClazz, HttpCallback callback) {
    
            long startTime = System.currentTimeMillis();
    
            Result result = new Result();
            try {
    
                //初始化上下文，
                ContextHolder.init();
                ContextHolder.setClientIp(request.getRequestURI());
    
                //打印请求日志
                logRequest(request);
    
                //入参检查
                callback.checkParameter();
    
                //业务执行，返回业务结果
                result = callback.execute();
    
            } catch (CustomException e) {
    
                result = handleBizException(e, resultClazz);
    
            } catch (Throwable e) {
    
                result = handleSystemException(e, resultClazz);
    
            } finally {
    
                //耗时统计
                long costTime = System.currentTimeMillis() - startTime;
    
                //打印执行日志，一般用于发给日志平台/大数据平台，可自行扩展
                log.info(buildLog(request, result.success(), result.success() ? null : String.valueOf(result.getStatus()), costTime, result.getData().toString()));
    
                ContextHolder.clear();
            }
    
            return result;
        }
    
        private void logRequest(HttpServletRequest request) {
            log.info("请求接口：{}，请求参数：{}", request.getRequestURI(), buildParams(request.getParameterMap()));
        }
    
        private String buildParams(Map<String, String[]> param) {
            if (CollectionUtils.isEmpty(param)) {
                return "";
            }
            StringBuilder sb = new StringBuilder();
            param.forEach((k, v) -> {
                sb.append(k + ":" + Arrays.asList(v)).append(",");
            });
            return org.apache.commons.lang3.StringUtils.substringBeforeLast(sb.toString(), ",");
        }
    
        private String buildLog(HttpServletRequest request, boolean isSuccess, String resultCode, long costTime, String data) {
            StringBuilder sb = new StringBuilder("[");
            sb.append(request.getRequestURI()).append(COMMA);
            sb.append(isSuccess ? "S" : "F").append(COMMA);
            sb.append(StringUtils.defaultIfBlank(resultCode, NULL_REPLACE)).append("]");
            sb.append("(").append(costTime).append("ms)").append(COMMA);
            sb.append("result：").append(data);
            return sb.toString();
        }
    
        private Result handleBizException(CustomException bizEx, Class<? extends Result> resultClazz) {
            log.warn("biz errorcode occurred：{}", bizEx.getMessage());
            try {
                Result result = resultClazz.newInstance();
                result.setStatus(1001);
                result.setMessage("业务异常，用户不存在，一般为枚举");
                return result;
            } catch (Throwable t) {
                log.error("new instance error, class: {},throwable：{}", resultClazz.getClass(), t);
                return null;
            }
        }
    
        private Result handleSystemException(Throwable e, Class<? extends Result> resultClazz) {
            if (e instanceof IllegalArgumentException) {
                log.warn("parameter illegal: {}", e.getMessage());
            } else {
                log.error("unknown exception");
            }
            try {
                Result result = resultClazz.newInstance();
                result.setStatus(500);
                result.setMessage("系统错误");
                return result;
            } catch (Throwable t) {
                log.error("new instance error, class: {},throwable：{}", resultClazz.getClass(), t);
                return null;
            }
        }
    }

###  模板里用到的上下文ContextHolder ###

/**
     * 上下文
     */
    public class ContextHolder {
    
        private static ThreadLocal<Context> contextHolder = new ThreadLocal<Context>();
    
        /**
         * 请求入口的地方调这里初始化上下文
         */
        public static void init() {
            contextHolder.set(new Context());
        }
    
        /**
         * 清理上下文，一定要清理，避免内存泄漏
         */
        public static void clear() {
            contextHolder.get().clean();
            contextHolder.set(null);
            contextHolder.remove();
        }
    
        public static void setContext(Context context) {
            Assert.notNull(context);
            contextHolder.set(context);
        }
    
        public static Context getContext() {
            if (contextHolder.get() == null) {
                contextHolder.set(new Context());
            }
            return contextHolder.get();
        }
    
        public static void setUserId(Long userId) {
            getContext().setUserId(userId);
        }
    
        public static void getUserId() {
            getContext().getUserId();
        }
    
        public static void setClientIp(String clientIp) {
            getContext().setClientIp(clientIp);
        }
    
        public static void getClientIp() {
            getContext().getClientIp();
        }
        
    }

###  Controller ###

里面只有字段检查和业务执行的逻辑，其他的事情走交给模板去做了，是不是比较简洁呀

@RestController
    public class TestHttpTemplateController {
    
        @Resource
        private HttpTemplate httpTemplate;
    
        @Resource
        private UserService userService;
    
        @RequestMapping("/test")
        public Result queryUser(HttpServletRequest request) {
    
            return httpTemplate.execute(request, Result.class, new HttpCallback() {
    
                @Override
                protected void checkParameter() {
                    Assert.notNull(request.getParameter("userId"));
                }
    
                @Override
                protected Result execute() {
                    return userService.findById(Long.valueOf(request.getParameter("userId")));
                }
    
            });
        }
    }

### Service ###

@Service
    public class UserServiceImpl implements UserService {
    
        @Override
        public Result findById(Long userId) {
    
            UserVO vo = new UserVO();
    
            vo.setUserId(100L);
            vo.setUsername("maple");
    
            if (vo == null) {
                throw new CustomException("user not exist");
            }
    
            List<Fans> list = new ArrayList<>();
            Fans fans = new Fans(100L, "张三");
            list.add(fans);
    
            fans = new Fans(200L, "李四");
            list.add(fans);
    
            vo.setFansList(list);
    
            return new Result(vo);
    
        }
    }

项目启动，浏览器里输入：[http://localhost:8080/test?userId=1&&username=maple][http_localhost_8080_test_userId_1_username_maple]

测试结果为：

![2019120518380148.png][]

思路给大家了，可自行扩展。谢谢

[http_localhost_8080_test_userId_1_username_maple]: http://localhost:8080/test?userId=1&&username=maple
[2019120518380148.png]: /images/1602083600654.png