springmvc图片上传及json数据转换过程详解

一、springmvc图片上传过程详解

1.在pom.xml文件中添加以下依赖

<dependency>
    <groupId>commons-fileupload</groupId>
    <artifactId>commons-fileupload</artifactId>
    <version>1.4</version>
</dependency>

2.在springmvc.xml中添加以下配置

<!--文件上传配置-->
<bean id="multipartResolver"
      class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
    <property name="defaultEncoding" value="UTF-8"/>
    <property name="maxUploadSize" value="2097152"/>
    <property name="maxInMemorySize" value="1048576"/>
    <!--默认上传临时文件目录-->
    <property name="uploadTempDir">
        <bean class="org.springframework.web.multipart.commons.CommonsMultipartFile"
              factory-bean="fileItemFactory"
              factory-method="getUploadDir"/>
    </property>
</bean>

<!--文件上传工厂类-->
<bean id="fileItemFactory" class="org.apache.commons.fileupload.disk.DiskFileItemFactory">
    <property name="repository"
              value="D:/temp/upload"/>
    <!--上传文件大于10KB时生成新的临时文件-->
    <property name="sizeThreshold"
              value="10240"/>
</bean>

3.在controller中添加以下代码

@RequestMapping("/upload")
public String upload(@RequestParam("file") MultipartFile file,
                     HttpServletRequest request) {
    //检查文件是否为空
    if (!file.isEmpty()) {
        try {
            //保存文件
            String filename = file.getOriginalFilename();
            String path = request.getSession().getServletContext()
                          .getRealPath("upload/" + filename);
            file.transferTo(new File(path));
            return "上传成功";
        } catch (Exception e) {
            e.printStackTrace();
            return "上传失败";
        }
    } else {
        return "文件为空";
    }
}

二、json数据转换过程详解

1.在pom.xml文件中添加以下依赖

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.13.0</version>
</dependency>

2.在controller中添加以下代码

@RequestMapping("/json")
@ResponseBody
public Map<String, Object> json() {
    Map<String, Object> map = new HashMap<>();        map.put("name", "Tom");
    map.put("age", 18);
    return map;
}

3.访问json接口，可以看到返回的数据格式为json

{
    "name": "Tom",
    "age": 18
}

示例1：springmvc图片上传

1.上传文件的html代码段

<form method="POST" action="/upload" enctype="multipart/form-data">
    <input type="file" name="file"/>
    <button type="submit">上传</button>
</form>

2.上传文件的controller

@RequestMapping("/upload")
@ResponseBody
public String upload(@RequestParam("file") MultipartFile file,
                     HttpServletRequest request) {
    //检查文件是否为空
    if (!file.isEmpty()) {
        try {
            //保存文件
            String filename = file.getOriginalFilename();
            String path = request.getSession().getServletContext()
                          .getRealPath("upload/" + filename);
            file.transferTo(new File(path));
            return "上传成功";
        } catch (Exception e) {
            e.printStackTrace();
            return "上传失败";
        }
    } else {
        return "文件为空";
    }
}

示例2：json数据转换

1.获取json数据的html代码段

<button type="button" onclick="getJson()">获取Json数据</button>
<script>
    function getJson() {
        $.ajax({
            url: "/json",
            type: "GET",
            dataType: "json",
            success: function (data) {
                alert(JSON.stringify(data))
            },
            error: function () {
                alert("获取数据失败")
            }
        })
    }
</script>

2.获取json数据的controller

@RequestMapping("/json")
@ResponseBody
public Map<String, Object> json() {
    Map<String, Object> map = new HashMap<>();
    map.put("name", "Tom");
    map.put("age", 18);
    return map;
}