springmvc图片上传及json数据转换过程详解

springmvc的图片上传

1.导入相应的pom依赖

 <dependency>
   <groupId>commons-fileupload</groupId>
   <artifactId>commons-fileupload</artifactId>
   <version>1.3.3</version>
  </dependency>

2.添加springmvc-servlet.xml里面的配置

<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
    <!-- 必须和用户JSP 的pageEncoding属性一致，以便正确解析表单的内容 -->
    <property name="defaultEncoding" value="UTF-8"></property>
    <!-- 文件最大大小(字节) 1024*1024*50=50M-->
    <property name="maxUploadSize" value="52428800"></property>
    <!--resolveLazily属性启用是为了推迟文件解析，以便捕获文件大小异常-->
    <property name="resolveLazily" value="true"/>
  </bean>

3.前台文件上传表单

<%--
 Created by IntelliJ IDEA.
 User: ASUS
 Date: 2019/10/5
 Time: 10:25
 To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
  <title>文件上传</title>
</head>
<body>
  <form action="${pageContext.request.contextPath}/upload" method="post" enctype="multipart/form-data">
    上传的文件：<input type="file" name="img" id="">
    <button type="submit">提交</button>
  </form>
</body>
</html>

HelloController

/**
   * 文件上传
   * @param img
   * @return
   */
  @RequestMapping("/upload")
  public String upload(MultipartFile img){
    try {
      FileUtils.copyInputStreamToFile(img.getInputStream(),new File("F:/xxx/"+img.getOriginalFilename()));
    } catch (IOException e) {
      e.printStackTrace();
    }
    return "forward:hello3";
  }

json数据转换

注解格式转换@ResponseBody

工具类JSONResult

package com.liuwenwu.util;

public class JSONResult {

  // 响应业务状态
  private Integer status;

  // 响应消息
  private String msg;

  // 响应中的数据
  private Object data;

  private String ok;  // 不使用

  public static JSONResult build(Integer status, String msg, Object data) {
    return new JSONResult(status, msg, data);
  }

  public static JSONResult ok(Object data) {
    return new JSONResult(data);
  }

  public static JSONResult ok() {
    return new JSONResult(null);
  }

  public static JSONResult errorMsg(String msg) {
    return new JSONResult(500, msg, null);
  }

  public static JSONResult errorMap(Object data) {
    return new JSONResult(501, "error", data);
  }

  public static JSONResult errorTokenMsg(String msg) {
    return new JSONResult(502, msg, null);
  }

  public static JSONResult errorException(String msg) {
    return new JSONResult(555, msg, null);
  }

  public JSONResult() {

  }

  public JSONResult(Integer status, String msg, Object data) {
    this.status = status;
    this.msg = msg;
    this.data = data;
  }

  public JSONResult(Object data) {
    this.status = 200;
    this.msg = "OK";
    this.data = data;
  }

  public Boolean isOK() {
    return this.status == 200;
  }

  public Integer getStatus() {
    return status;
  }

  public void setStatus(Integer status) {
    this.status = status;
  }

  public String getMsg() {
    return msg;
  }

  public void setMsg(String msg) {
    this.msg = msg;
  }

  public Object getData() {
    return data;
  }

  public void setData(Object data) {
    this.data = data;
  }

  public String getOk() {
    return ok;
  }

  public void setOk(String ok) {
    this.ok = ok;
  }

}

HelloController

@ResponseBody
  @RequestMapping("/jsonData3")
  public JSONResult jsonData3(){
    return JSONResult.ok("成功：这里可以存放字符串、对象、数组、集合都行，这样可以节省拼接map结合的过程");
  }

  @ResponseBody
  @RequestMapping("/jsonData4")
  public JSONResult jsonData4(){
    return JSONResult.errorMsg("失败：这里可以存放字符串、对象、数组、集合都行，这样可以节省拼接map结合的过程");
  }

效果：

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