【03】SpringMVC数据响应、文件上传、异常处理、拦截器

作者: 背对背拥抱 | 来源:发表于2019-11-28 16:30 被阅读0次

一、SpringMVC数据响应：

1）字符串响应：

jsp

<a href="/user/test" >testString</a>

Controller

@RequestMapping("/test")
    public String testUser(Model model){
        System.out.println("testUser。。。");

        User user = new User();
        user.setUsername("张三");
        user.setAge(55);
        user.setMoney(999d);
        model.addAttribute("user",user);
        return "success";
    }

2）void响应：

jsp:

<a href="/user/testVoid" >testVoid</a>

Controller:

@RequestMapping("/testVoid")
    public void testVoid(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("testVoid。。。");
        //请求转发
        //request.getRequestDispatcher("/WEB-INF/pages/success.jsp").forward(request,response);
        //重定向
        //response.sendRedirect(request.getContextPath()+"/index.jsp");

        //直接响应
        response.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");
        response.getWriter().write("你好啊...");
    }

3）ModelAndView响应：

存到了request域中

访问jsp

<a href="/user/testModelAndView" >testModelAndView</a>

Controller

@RequestMapping("/testModelAndView")
    public ModelAndView testUser(){
        System.out.println("testModelAndView。。。");
        ModelAndView mv = new ModelAndView();
        User user = new User();
        user.setUsername("李四");
        user.setAge(11);
        user.setMoney(222d);

        mv.addObject("user",user);
        mv.setViewName("success");

        return mv;
    }

结果jsp

${requestScope.username}

4）关键字forward/redirect转发：

jsp

<a href="/user/testForwardOrRedirect" >测试关键字转发/重定向</a>

Controller

 @RequestMapping("/testForwardOrRedirect")
    public String testForwardOrRedirect(){
        System.out.println("testForwardOrRedirect。。。");

        //return "forward:/WEB-INF/pages/success.jsp";
        return "redirect:/index.jsp";
    }

5）ResponseBody注解响应json数据

作用：该注解用于将Controller的方法返回的对象，通过HttpMessageConverter接口转换为指定格式的数据如：json,xml等，通过Response响应给客户端

Springmvc默认用MappingJacksonHttpMessageConverter对json数据进行转换，需要加入jackson的包。

 <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-databind</artifactId>
      <version>2.9.0</version>
    </dependency>
    <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-core</artifactId>
      <version>2.9.0</version>
    </dependency>
    <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-annotations</artifactId>
      <version>2.9.0</version>
    </dependency>

jsp

<script src="js/jquery.min.js"></script>
    <script type="text/javascript">
        $(function () {
            $("#btn").click(function () {
                $.ajax({
                    url:"user/testAjax",
                    dataType:"json",
                    contentType:"application/json;charset=UTF-8",
                    data:'{"username":"王丽丽","age":18,"money":200}',
                    type:"post",
                    success:function (data) {
                        alert(data.username+"---"+data.money);
                    }
                });
            });
        });
    </script>

Controller

 @RequestMapping("/testAjax")
    public @ResponseBody User testAjax(@RequestBody User user){
        System.out.println("testAjax。。。");
        System.out.println(user);
        user.setUsername("周XX");
        user.setMoney(99999d);
        return user;
    }

二、文件上传：

需要导入依赖：

<dependency>
      <groupId>commons-fileupload</groupId>
      <artifactId>commons-fileupload</artifactId>
      <version>1.3.1</version>
    </dependency>
    <dependency>
      <groupId>commons-io</groupId>
      <artifactId>commons-io</artifactId>
      <version>2.4</version>
    </dependency>

1）传统方式上传文件：

jsp

<form action="/fileupload/upload1" method="post" enctype="multipart/form-data">
        选择文件：<input type="file" name="upload"><br />
        <input type="submit" value="上传">
    </form>

Controller:

/**
     * 传统方式上传文件
     * @return
     */
    @RequestMapping("upload1")
    public String testUpload1(HttpServletRequest request){
        System.out.println("upload1");

        //上传的路径
        String path = request.getSession().getServletContext().getRealPath("/uploads/");

        //判断文件夹是否存在
        File file = new File(path);
        if(!file.exists()){
            //新建文件夹
            file.mkdirs();
        }

        //解析request对象，获取上传文件项
        DiskFileItemFactory factory = new DiskFileItemFactory();
        ServletFileUpload upload = new ServletFileUpload(factory);
        //解析request
        List<FileItem> items = null;
        try {
            items = upload.parseRequest(request);
            //遍历items
            for (FileItem item:items) {
                //进行判断，当前item对象是否是上传文件项
                if(item.isFormField()){
                    //普通表单项
                }else{
                    //上传文件项
                    //获取上传文件的名称
                    String fileName = item.getName();
                    String uuid = UUID.randomUUID().toString().replace("-", "");
                    fileName = uuid+"_"+fileName;

                    //上传文件
                    item.write(new File(path,fileName));
                    //删除临时文件
                    item.delete();
                }
            }
        } catch (FileUploadException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return "success2";
    }

配置文件解析器
在springmvc中配置:

<!--  配置文件解析器 : id的值是固定的-->
<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
    <!-- 设置上传文件的最大尺寸为5MB --> 
    <property name="maxUploadSize"> <value>5242880</value> </property>
</bean>

2）spingmvc方式上传文件：

jsp

<form action="/fileupload/upload2" method="post" enctype="multipart/form-data">
        选择文件：<input type="file" name="upload"><br />
        <input type="submit" value="上传">
    </form>

Controller:

/**
     * SpringMVC方式上传文件
     * @return
     */
    @RequestMapping("upload2")
    public String testUpload2(HttpServletRequest request, MultipartFile upload){
        System.out.println("upload2");

        //上传的路径
        String path = request.getSession().getServletContext().getRealPath("/uploads/");

        //判断文件夹是否存在
        File file = new File(path);
        if(!file.exists()){
            //新建文件夹
            file.mkdirs();
        }
        String fileName = upload.getOriginalFilename();
        String uuid = UUID.randomUUID().toString().replace("-", "");
        fileName = uuid+"_"+fileName;

        //上传文件
        try {
            upload.transferTo(new File(path,fileName));
        } catch (IOException e) {
            e.printStackTrace();
        }
        return "success2";
    }

3）springmvc方式实现跨服务器上传：

需要在文件上传的依赖基础之上，再导入另外两个依赖：
这两个依赖是sun公司提供的。

<dependency>
      <groupId>com.sun.jersey</groupId>
      <artifactId>jersey-core</artifactId>
      <version>1.18.1</version>
    </dependency>
    <dependency>
      <groupId>com.sun.jersey</groupId>
      <artifactId>jersey-client</artifactId>
      <version>1.18.1</version>
    </dependency>

jsp

<form action="/fileupload/upload3" method="post" enctype="multipart/form-data">
        选择文件：<input type="file" name="upload"><br />
        <input type="submit" value="上传">
    </form>

Controller:

/**
     * SpringMVC方式上传文件
     * @return
     */
    @RequestMapping("upload3")
    public String testUpload3(MultipartFile upload){
        System.out.println("upload3");

        //上传的路径
        String path = "http://localhost:9090/uploads/";

        String fileName = upload.getOriginalFilename();
        String uuid = UUID.randomUUID().toString().replace("-", "");
        fileName = uuid+"_"+fileName;

        //创建客户端对象
        Client client = Client.create();
        //和文件服务器进行连接
        WebResource webResource = client.resource(path + fileName);

        try {
            //上传文件
            webResource.put(upload.getBytes());
        } catch (IOException e) {
            e.printStackTrace();
        }
        return "success2";
    }

三、异常处理：

系统中异常包括两类：预期异常和运行时异常RuntimeException，前者通过捕获异常从而获取异常信息，后者主要通过规范代码开发、测试通过手段减少运行时异常的发生。
系统的dao、service、controller出现都通过throws Exception向上抛出，最后由springmvc前端控制器交由异常处理器进行异常处理，如下图：

实现步骤：

1）编写异常类和错误页面

异常类：

package com.zl.except;

public class SysException extends Exception{
    private String exceptionMsg;

    public SysException(String exceptionMsg) {
        this.exceptionMsg = exceptionMsg;
    }

    public String getExceptionMsg() {
        return exceptionMsg;
    }

    public void setExceptionMsg(String exceptionMsg) {
        this.exceptionMsg = exceptionMsg;
    }
}

错误页面error.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" isELIgnored="false" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    <h3>错误页面...</h3>
    ${errorMsg}
</body>
</html>

2）自定义异常处理器

package com.zl.except;

import org.springframework.web.servlet.HandlerExceptionResolver;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class SysExceptionResolver implements HandlerExceptionResolver {
    @Override
    public ModelAndView resolveException(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) {
        SysException ex = null;
        if(e instanceof SysException){
            ex = (SysException) e;
        }else{
            ex = new SysException("系统正在维护中....");
        }
        ModelAndView mv = new ModelAndView();
        mv.addObject("errorMsg",ex.getExceptionMsg());
        mv.setViewName("error");
        return mv;
    }
}

3）配置异常处理器

在springmvc.xml中配置异常处理器：

 <!--配置异常处理器-->
 <bean id="sysExceptionResolver" class="com.zl.except.SysExceptionResolver"></bean>

4）编写Controller类：

package com.zl.controller;

import com.zl.except.SysException;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
@RequestMapping("exception")
public class ExceptionController {

    @RequestMapping("testException")
    public String testException() throws SysException {
        System.out.println("testException");
        try {
            int i = 10/0;
        } catch (Exception e) {
            e.printStackTrace();
            throw new SysException("查找用户出错...");
        }
        return "success";
    }
}

四、SpingMVC拦截器：

1）自定义拦截器，实现HandlerInterceptor接口

MyInterceptor1

package com.zl.interceptor;

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class MyInterceptor1 implements HandlerInterceptor {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("MyInterceptor1....前111");
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("MyInterceptor1....后111");
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("MyInterceptor1....最后111");
    }
}

MyInterceptor2

package com.zl.interceptor;

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class MyInterceptor2 implements HandlerInterceptor {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("MyInterceptor1....前222");
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("MyInterceptor1....后222");
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("MyInterceptor1....最后222");
    }
}

2）配置拦截器

在springmvc.xml中配置

<!--配置拦截器-->
    <mvc:interceptors>
        <mvc:interceptor>
            <mvc:mapping path="/interceptor/*"/>
            <bean class="com.zl.interceptor.MyInterceptor1"/>
        </mvc:interceptor>
        <mvc:interceptor>
            <mvc:mapping path="/**"/>
            <bean class="com.zl.interceptor.MyInterceptor2"/>
        </mvc:interceptor>
    </mvc:interceptors>

interceptor.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    <a href="/interceptor/testInterceptor">测试拦截器</a>
</body>
</html>

Controller

package com.zl.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
@RequestMapping("interceptor")
public class InterceptorController {

    @RequestMapping("testInterceptor")
    public String testInterceptor(){
        System.out.println("testInterceptor...");
        return "success";
    }
}

需要注意的是：如果配置了多个拦截器，执行顺序如下：

【03】SpringMVC数据响应、文件上传、异常处理、拦截器

一、SpringMVC数据响应：

1）字符串响应：

2）void响应：

3）ModelAndView响应：

4）关键字forward/redirect转发：

5）ResponseBody注解响应json数据

二、文件上传：

1）传统方式上传文件：

2）spingmvc方式上传文件：

3）springmvc方式实现跨服务器上传：

三、异常处理：

1）编写异常类和错误页面

2）自定义异常处理器

3）配置异常处理器

4）编写Controller类：

四、SpingMVC拦截器：

1）自定义拦截器，实现HandlerInterceptor接口

2）配置拦截器

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