Spring统一功能处理

1. AOP存在的问题

获取参数复杂
AOP的规则相对简单

2. 拦截器

2.1. 应用(以登录为例)

2.1.1. 自定义拦截器

新建interceptor文件夹

import org.springframework.web.servlet.HandlerInterceptor;import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;@Component
public class LoginInterceptor implements HandlerInterceptor {@Overridepublic boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {//判断是否登录HttpSession session = request.getSession(false);if (session!=null && session.getAttribute("username")!=null){//通过return true;}else {//没登录response.setStatus(401);return false;}}
}

2.1.2. 将自定义拦截器加入到系统配置

新建config文件夹

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
import springaop.interceptor.LoginInterceptor;@Configuration
public class AppConfig implements WebMvcConfigurer {@Autowiredprivate LoginInterceptor loginInterceptor;@Overridepublic void addInterceptors(InterceptorRegistry registry) {registry.addInterceptor(loginInterceptor).addPathPatterns("/**")         //"/**"表示拦截所有.excludePathPatterns("/user/login")  //除了登录.excludePathPatterns("/user/reg");    //除了注册}
}

2.1.3. 业务代码

import lombok.extern.slf4j.Slf4j;
import org.springframework.util.StringUtils;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;@Slf4j
@RequestMapping("/user")
@RestController
public class UserController {//获取用户信息@RequestMapping("/getInfo")public String getInfo(){log.info("log.getInfo");return "get info...";}//注册@RequestMapping("/reg")public String reg(){log.info("log.reg");return "reg...";}//登录@RequestMapping("/login")public boolean login(HttpServletRequest request,String username,String password){log.info("log.login");//判断username和password是否为空
//        if (username!=null && username.equals("") && password!=null && password.equals("")){
//            //
//        }if (!StringUtils.hasLength(username) || !StringUtils.hasLength(password)){return false;}if (!"admin".equals(username) || !"admin".equals(password)){return false;}HttpSession session = request.getSession(true);session.setAttribute("username",username);return true;}
}

2.2. 排除所有静态资源方法

方法1

registry.addInterceptor(new LoginInterceptor()).addPathPatterns("/**") // 拦截所有接口.excludePathPatterns("/**/*.js").excludePathPatterns("/**/*.css").excludePathPatterns("/**/*.jpg").excludePathPatterns("/login.html").excludePathPatterns("/**/login"); // 排除接口

方法2

private final List<String> excludePaths = //注意List的这种方式的初始化赋值不允许再追加元素Arrays.asList("/**/*.html","blog-editormd","/css/**","/js/**","/pic/**","/user/login","/user/res");@Overridepublic void addInterceptors(InterceptorRegistry registry) {registry.addInterceptor(loginInterceptor).addPathPatterns("/**").excludePathPatterns(excludePaths);}

2.3. 实现原理

2.3.1. 总体思路

2.3.2. 部分源码分析

拦截器是基于AOP实现的

(AOP基于动态代理(JDK|CGLIB))

3. 统一功能处理

3.1. 统一登录处理

参考上一节拦截器的应用

3.2. 统一异常处理

对于下面的异常, 我们在访问页面的时候,不希望让用户看到

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;@RestController
@RequestMapping("/exception")
public class ExceptionController {//算数异常@RequestMapping("/test1")public boolean test1(){int a = 10/0;return true;}//空指针异常@RequestMapping("/test2")public boolean test2(){String str = null;System.out.println(str.length());return true;}//手动异常@RequestMapping("/test3")public boolean test3(){throw new RuntimeException("手动异常");}
}

可能出现的问题:

类上面的@RequestMapping("/ex")访问的时候会有未知的问题,改成@RequestMapping("/exception")比较好

3.2.1. 配置ErrorHandler

针对不同的异常,进行不同的操作

import lombok.extern.slf4j.Slf4j;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.ResponseBody;import java.util.HashMap;@Slf4j
@ControllerAdvice
@ResponseBody
public class ErrorHandler {@ExceptionHandlerpublic Object error(Exception e){HashMap<String,Object> result = new HashMap<>();log.info("内部异常:",e);result.put("success",0);result.put("code",-1);result.put("msg","内部异常");return result;}@ExceptionHandlerpublic Object error(ArithmeticException e){HashMap<String,Object> result = new HashMap<>();log.info("算数异常:",e);result.put("success",0);result.put("code",-2);result.put("msg","算术异常");return result;}@ExceptionHandlerpublic Object error(NullPointerException e){HashMap<String,Object> result = new HashMap<>();log.info("空指针异常:",e);result.put("success",0);result.put("code",-3);result.put("msg","空指针异常");return result;}
}

3.2.1.1. 可能会遇到的问题

①写完代码访问的时候,会是错误404, 而且异常是返回的不是一个视图, 需要添加@ResponseBody注解,让程序意识到返回的就是数据, 而不是视图

②分辨不出来异常

之前在切面的@Around环绕通知里有一段代码

要是遇到了异常都会抛出RuntimeException, 从而掩盖了真正的异常, 需要改成下面的样子, 抛出真正的异常

3.3. 统一数据返回格式

3.3.1. 好处

统一数据返回格式的优点有很多. 比如以下几个:

方便前端程序员更好的接收和解析后端数据接口返回的数据
降低前端程序员和后端程序员的沟通成本，按照某个格式实现就行了，因为所有接口都是这样返回的
有利于项目统一数据的维护和修改
有利于后端技术部门的统一规范的标准制定，不会出现稀奇古怪的返回内容

3.3.2. 代码

新建ResponseHandler

import org.springframework.core.MethodParameter;
import org.springframework.http.MediaType;
import org.springframework.http.server.ServerHttpRequest;
import org.springframework.http.server.ServerHttpResponse;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.servlet.mvc.method.annotation.ResponseBodyAdvice;import java.util.HashMap;@ControllerAdvice
public class ResponseHandler implements ResponseBodyAdvice {@Overridepublic boolean supports(MethodParameter returnType, Class converterType) {return true;    //一定要改成true}@SneakyThrows@Overridepublic Object beforeBodyWrite(Object body, MethodParameter returnType, MediaType selectedContentType, Class selectedConverterType, ServerHttpRequest request, ServerHttpResponse response) {HashMap<String,Object> result = new HashMap<>();result.put("success",1);result.put("data",body);result.put("errMsg","");//对字符串进行特殊处理if (body instanceof String){ObjectMapper mapper = new ObjectMapper();return mapper.writeValueAsString(result);}return result;}
}

添加这段代码之前, 访问成功了,得到的是true, 加上这段代码就变成了{"data":true,"success":1,"errMsg":""}