springboot day4 异常处理与servlet3.0注解过滤器

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1 异常处理

类添加注解

@ControllerAdvice ，如果需要返回 json 数据，则⽅法需要加 @ResponseBody

@RestControllerAdvice, 默认返回 json 数据，⽅法不需要加 @ResponseBody

⽅法添加处理器

捕获全局异常 , 处理所有不可知的异常

@ExceptionHandler(value=Exception.class)

package com.test.utils;/*** 接口返回工具类*/
public class JsonData {private int code;private Object data;private String msg;public int getCode() {return code;}public void setCode(int code) {this.code = code;}public Object getData() {return data;}public void setData(Object data) {this.data = data;}public String getMsg() {return msg;}public void setMsg(String msg) {this.msg = msg;}public JsonData(){}public JsonData(int code, Object data){this.code = code;this.data = data;}public JsonData(int code, Object data, String msg){this.code = code;this.data =data;this.msg = msg;}public static JsonData buildSuccess(Object data){return new JsonData(0,data);}public static JsonData buildError(String msg){return new JsonData(-1,"",msg);}public static JsonData buildError(String msg,int code){return new JsonData(code,"",msg);}@Overridepublic String toString() {return "JsonData{" +"code=" + code +", data=" + data +", msg='" + msg + '\'' +'}';}
}/*** 标记这是个异常处理类*/
@RestControllerAdvice
public class CustomExtHandler {@ExceptionHandler(value = Exception.class)JsonData handlerException(Exception e, HttpServletRequest request){return JsonData.buildError("服务端出问题了", -2);}
}

2 ⾃定义全局异常返回⻚⾯

返回⾃定义异常界⾯，需要引⼊ thymeleaf 依赖 ( ⾮必须，如果是简单的 html 界⾯则不⽤ )

<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>

resource ⽬录下新建 templates, 并新建 error.html

ModelAndView modelAndView = new ModelAndView();
modelAndView.setViewName("error.html");
modelAndView.addObject("msg", e.getMessage());
return modelAndView;

3. 过滤器

SpringBoot2.X ⾥⾯的过滤器

ApplicationContextHeaderFilter

OrderedCharacterEncodingFilter

OrderedFormContentFilter

OrderedRequestContextFilter

Ordered.HIGHEST_PRECEDENCE Ordered.LOWEST_PRECEDENCE

低位值意味着更⾼的优先级 Higher values are interpreted as lower priority

⾃定义 Filter ，避免和默认的 Filter 优先级⼀样，不然会冲突

bean FilterRegistrationBean

Servlet3.0 webFileter

使⽤Servlet3.0的注解进⾏配置步骤

启动类⾥⾯增加 @ServletComponentScan ，进⾏扫描

新建⼀个Filter 类， implements Filter ，并实现对应的接⼝

@WebFilter 标记⼀个类为 fifilter ，被 spring 进⾏扫描

urlPatterns：拦截规则，⽀持正则

控制chain.doFilter 的⽅法的调⽤，来实现是否通过放⾏

不放⾏，web 应⽤ resp.sendRedirect("/index.html") 或者返回 json 字符串

权限控制、⽤户登录状态控制，也可以交给拦截器处理等

@WebFilter(urlPatterns = "/api/v1/pri/*", filterName = "loginFilter")
public class LoginFilter implements Filter {/*** 容器加载的时候* @param filterConfig* @throws ServletException*/@Overridepublic void init(FilterConfig filterConfig) throws ServletException {System.out.println("init LoginFilter======");}@Overridepublic void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {System.out.println("doFilter LoginFilter======");HttpServletRequest req = (HttpServletRequest) servletRequest;HttpServletResponse resp = (HttpServletResponse) servletResponse;String token = req.getHeader("token");if(StringUtils.isEmpty(token)){token = req.getParameter("token");}if(StringUtils.isEmpty(token)){return;}else {//判断token是否合法}}/*** 容器销毁的时候*/@Overridepublic void destroy() {System.out.println("destroy LoginFilter======");}
}

Servlet3.0返回未登录错误码

private void renderJson(HttpServletResponse response,String json){response.setCharacterEncoding("UTF-8");response.setContentType("application/json");try(PrintWriter writer = response.getWriter()){writer.print(json);}catch (Exception e){e.printStackTrace();}
}

Servlet3.0注解开发原⽣Servlet更轻量级

@WebServlet(name = "userServlet", urlPatterns = "/api/v1/test/customs" )
class UserServlet extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {PrintWriter writer = resp.getWriter();writer.write("this is my custom servlet");writer.flush();writer.close();}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {this.doGet(req,resp);}
}

Servlet3.0+SpringBoot2.X 注解Listener常⽤监听器

监听器：应⽤启动监听器，会话监听器，请求监听器

ServletContextListener 应⽤启动监听

HttpSessionLisener 会话监听（前后端分离架构不再用）

ServletRequestListener 请求监听

@WebListener
public class RequestListener implements ServletRequestListener {@Overridepublic void contextDestroyed(ServletContextEvent sce) {System.out.println("======contextDestroyed========");}@Overridepublic void contextInitialized(ServletContextEvent sce) {System.out.println("======contextInitialized========");}
}

4 拦截器

SpringBoot2.x 使⽤步骤

SpringBoot2.X 新版本配置拦截器 implements WebMvcConfifigurer

⾃定义拦截器 HandlerInterceptor

preHandle：调⽤Controller 某个⽅法之前

postHandle：Controller 之后调⽤，视图渲染之前，如果控制器 Controller 出现了异常，则不会执⾏此⽅法

afterCompletion：不管有没有异常，这个afterCompletion 都会被调⽤，⽤于资源清理

按照注册顺序进⾏拦截，先注册，先被拦截

注意

-是否有加 @Configuration

-拦截路径是否有问题 ** 和 *

-拦截器最后路径⼀定要 /** 如果是⽬录的话则是 /*/

Filter和 Interceptor ⼆者都是 AOP 编程思想的体现，功能基本都可以实现

拦截器功能更强⼤些，Filter 能做的事情它都能做

Filter在只在 Servlet 前后起作⽤，⽽ Interceptor 够深⼊到⽅法前后、异常抛出前后等

filter依赖于 Servlet 容器即 web 应⽤中，⽽ Interceptor 不依赖于 Servlet 容器所以可以运⾏在多种环境。

在接⼝调⽤的⽣命周期⾥，Interceptor 可以被多次调⽤，⽽ Filter 只能在容器初始化时调⽤⼀次。

Filter和 Interceptor 的执⾏顺序

过滤前->拦截前 ->action 执⾏ -> 拦截后 -> 过滤后

配置不拦截路径

registry.addInterceptor(new LoginIntercepter()).addPathPatterns("/api/v1/pri/**")

// 配置不拦截某些路径，⽐如静态资源

.excludePathPatterns("/**/*.html","/**/*.js");

5 SpringBoot2.X 整合模板引擎

JSP（后端渲染，消耗性能）

Freemarker

Freemarker 相关 maven 依赖

<!-- 引⼊freemarker模板引擎的依赖 --><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-freemarker</artifactId></dependency>

Freemarker 基础配置

 # 是否开启thymeleaf缓存,本地为false，⽣产建议为truespring.freemarker.cache=falsespring.freemarker.charset=UTF-8spring.freemarker.allow-request-override=falsespring.freemarker.check-template-location=true#类型spring.freemarker.content-type=text/htmlspring.freemarker.expose-request-attributes=truespring.freemarker.expose-session-attributes=true#⽂件后缀spring.freemarker.suffix=.ftl#路径spring.freemarker.template-loader-path=classpath:/templates/

Thymeleaf

thymeleaf相关maven依赖

<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>

thymeleaf 基础配置

#开发时关闭缓存,不然没法看到实时⻚⾯spring.thymeleaf.cache=falsespring.thymeleaf.mode=HTML5#前缀spring.thymeleaf.prefix=#编码spring.thymeleaf.encoding=UTF-8#类型spring.thymeleaf.content-type=text/html#名称的后缀spring.thymeleaf.suffix=.html

Getting started with the Standard dialects in 5 minutes - Thymeleaf

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