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);
    }


    @Override
    public 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
     */
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

        System.out.println("init LoginFilter======");
    }



    @Override
    public 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
     */
    @Override
    public 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 {
 @Override
 protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
 PrintWriter writer = resp.getWriter();
 writer.write("this is my custom servlet");
 writer.flush();
 writer.close();
 }
 @Override
 protected 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 {
 @Override
 public void contextDestroyed(ServletContextEvent sce) {
 System.out.println("======contextDestroyed========");
 }
 @Override
 public 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true
 spring.freemarker.cache=false
 spring.freemarker.charset=UTF-8
 spring.freemarker.allow-request-override=false
 spring.freemarker.check-template-location=true
 
 #类型
 spring.freemarker.content-type=text/html
 spring.freemarker.expose-request-attributes=true
 spring.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=false
 spring.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

原文链接：https://blog.csdn.net/u010173059/article/details/123075693