@RequsetMapping

@RequestMapping注解用于映射url到控制器类

package top.wmgx.controller;

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

@Controller
//@RequestMapping("/a")
public class Hello {
    //访问地址为(http://localhost:8081/a1)
    //若类前面有@RequestMapping("/a")访问地址为(http://localhost:8081/a/a1)
    @RequestMapping("/a1")
    public String test(Model model){
        model.addAttribute("msg","ok");
        return "test";
    }
}

参数接收

1. 普通参数

http://localhost:8081/a1?username=admin&pwd=123456

@Controller
public class Hello {
    //名称一致的可以直接写
    //名称不一致的加@RequestParam("pwd") 注解
    //建议一致或者不一致都写@RequestParam() 
     @RequestMapping("/a1")
    public String test(String name, @RequestParam("pwd") String password){
        System.out.println(name+"\n"+password);
        return "test";
    }
}

2. 接受方也可以是对象

前提，对象的属性和前端必须保持一致提供set方法

package top.wmgx.Model;
public class User {
    private String name;
    private String pwd;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }
    @Override
    public String toString() {
        return "User{" +
                "name='" + name + '\'' +
                ", pwd='" + pwd + '\'' +
                '}';
    }
}

@Controller
public class Hello {
    //可以直接写User user 对应属性会被设置进去，没有的会为null
     @RequestMapping("/a1")
    public String test(User user){
        System.out.println(user);
        return "test";
    }
}

3. HttpServletRequest

@Controller
public class Hello {
    //可以直接写User user 对应属性会被设置进去，没有的会为null
     @RequestMapping("/a1")
    public String test(HttpServletRequest request){
        String name = request.getParameter("name");              String pwd = request.getParameter("pwd");
        System.out.println(name+"\n"+password);
        return "test";
    }
}

4. RestFul

参数在路径中，上方的链接变成了

http://localhost:8081/a1/admin/123456

url含有中文名称时，因为编码问题，无法进行映射，需要修改tomcat下的conf文件夹下的server.xml中的URIEncoding=”UTF-8”

@Controller
public class Hello {
    // 限制get请求并设置返回编码为utf-8
    @RequestMapping(value = "/a1/{name}/{pwd}", method = RequestMethod.GET, produces = {"application/json;charset=UTF-8"})
    @ResponseBody
    public String test(@PathVariable String name, @PathVariable String pwd){
        System.out.println(name+"\n"+pwd);
        return "test";
    }
}

5. JSON方式

<!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind -->
  
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.10.2</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-core -->
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-core</artifactId>
            <version>2.10.2</version>
        </dependency>

需要导入jackson的支持，会被自动装配的配置项 <mvc:annotation-driven /> 装配

前端提示：HTTP Status 415 – 不支持的媒体类型

后端提示：Content type 'application/json' not supported]

前端发送的Header前面需要加上Content-Type:”application/json”

前端提示：HTTP Status 415 – 不支持的媒体类型

​ 描述源服务器拒绝服务请求，因为有效负载的格式在目标资源上此方法不支持。

@RequestMapping(value = "/a", method = {RequestMethod.POST},  consumes = {"application/json"})
    @ResponseBody
    public String test(@RequestBody User user){
        return user.toString();
    }

consumes设置后，只处理Content-Type:“application/json”的数据

组合注解

@GetMapping
@PostMapping
@PutMapping
@DeleteMapping
@PatchMapping

@GetMapping 等同于 @RequestMapping(method =RequestMethod.GET)

转发与重定向

• 在视图解析器中，默认就是转发
• 重定向的话 return "redirect:index.jsp"或者return "redirect:test1"另一个RequestMapping

拦截器

public class MyInterceptor implements HandlerInterceptor {

    //在请求处理的方法之前执行
    //如果返回true执行下一个拦截器
    //如果返回false就不执行下一个拦截器
    public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {
        System.out.println("------------处理前------------");
        return true;//true继续向下走
    }

    //在请求处理方法执行之后执行
    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {
        System.out.println("------------处理后------------");
    }

    //在dispatcherServlet处理后执行,做清理工作.
    public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {
        System.out.println("------------清理------------");
    }
}

配置文件

<!--关于拦截器的配置-->
<mvc:interceptors>
    <mvc:interceptor>
        <!--/** 包括路径及其子路径-->
        <!--/* 拦截的是/一级的-->
        <mvc:mapping path="/**"/>
        <!--bean配置的就是拦截器-->
        <bean class="top.wmgx.interceptor.MyInterceptor"/>
    </mvc:interceptor>
</mvc:interceptors>

文件上传

前端设置

enctype="multipart/form-data"

<form action="" enctype="multipart/form-data" method="post">
    <input type="file" name="file"/>
    <input type="submit">
</form>

导入jar包

<!--文件上传-->
<dependency>
    <groupId>commons-fileupload</groupId>
    <artifactId>commons-fileupload</artifactId>
    <version>1.3.3</version>
</dependency>
<!--servlet-api导入高版本的-->
<dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>javax.servlet-api</artifactId>
    <version>4.0.1</version>
</dependency>

配置sping配置文件

<!--文件上传配置-->
<bean id="multipartResolver"  class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
    <!-- 请求的编码格式，必须和jSP的pageEncoding属性一致，以便正确读取表单的内容，默认为ISO-8859-1 -->
    <property name="defaultEncoding" value="utf-8"/>
    <!-- 上传文件大小上限，单位为字节（10485760=10M） -->
    <property name="maxUploadSize" value="10485760"/>
    <property name="maxInMemorySize" value="40960"/>
</bean>

multipartResolver 命名一定是这个

代码

• String getOriginalFilename()：获取上传文件的原名
• InputStream getInputStream()：获取文件流
• void transferTo(File dest)：将上传文件保存到一个目录文件中

    //@RequestParam("file") 将得到的文件封装成CommonsMultipartFile 对象
    //批量上传CommonsMultipartFile则为数组即可
    @RequestMapping("/upload")
    public String Upload(@RequestParam("file") CommonsMultipartFile file , HttpServletRequest request) throws IOException {
        //获取文件名 : file.getOriginalFilename();
        String uploadFileName = file.getOriginalFilename();
        //如果文件名为空，直接回到首页！
        if ("".equals(uploadFileName)){
            return "redirect:/index.jsp";
        }
        System.out.println("上传文件名 : "+uploadFileName);
        //上传路径保存设置
        String path = request.getServletContext().getRealPath("/upload");
        //如果路径不存在，创建一个
        File realPath = new File(path);
        if (!realPath.exists()){
            realPath.mkdir();
        }
        System.out.println("上传文件保存地址："+realPath);
        InputStream is = file.getInputStream(); //文件输入流
        OutputStream os = new FileOutputStream(new File(realPath,uploadFileName)); //文件输出流
        //读取写出
        int len=0;
        byte[] buffer = new byte[1024];
        while ((len=is.read(buffer))!=-1){
            os.write(buffer,0,len);
            os.flush();
        }
        os.close();
        is.close();
        return "redirect:/index.jsp";
    }

利用file。Transto

/*
 * 采用file.Transto 来保存上传的文件
 */
@RequestMapping("/upload")
public String  upload(@RequestParam("file") CommonsMultipartFile file, HttpServletRequest request) throws IOException {
    //上传路径保存设置
    String path = request.getServletContext().getRealPath("/upload");
    File realPath = new File(path);
    if (!realPath.exists()){
        realPath.mkdir();
    }
    //上传文件地址
    System.out.println("上传文件保存地址："+realPath);

    //通过CommonsMultipartFile的方法直接写文件（注意这个时候）
    file.transferTo(new File(realPath +"/"+ file.getOriginalFilename()));

    return "redirect:/index.jsp";
}

下载

 @RequestMapping(value="/download")
    public String downloads(@RequestParam("file") String fileName,HttpServletResponse response , HttpServletRequest request) throws Exception{
        //要下载的图片地址
        String  path = request.getServletContext().getRealPath("/upload");
        //1、设置response 响应头
        response.reset(); //设置页面不缓存,清空buffer
        response.setCharacterEncoding("UTF-8"); //字符编码
        response.setContentType("multipart/form-data"); //二进制传输数据
        //设置响应头
        response.setHeader("Content-Disposition",
                "attachment;fileName="+ URLEncoder.encode(fileName, "UTF-8"));
        File file = new File(path,fileName);
        //2、 读取文件--输入流
        InputStream input=new FileInputStream(file);
        //3、 写出文件--输出流
        OutputStream out = response.getOutputStream();
        byte[] buff =new byte[1024];
        int index=0;
        //4、执行 写出操作
        while((index= input.read(buff))!= -1){
            out.write(buff, 0, index);
            out.flush();
        }
        out.close();
        input.close();
        return null;
    }