Example analysis of how Html5 implements asynchronous file upload function

This article briefly introduces the use of Html5's FormData to implement asynchronous uploading of files , and can also implement uploading progress bar and file size Verification, etc., the code is simple and easy to understand, very good, and has reference value. Friends who need it can refer to it

1 Introduction

DevelopingFile upload function is never a pleasant thing, especially asynchronous upload. I have used iframe and Flash upload solutions, and they all feel very good. awkward. This article briefly introduces the use of Html5's FormData to implement asynchronous uploading of files, and can also implement upload progress bars and file size verification. The server uses the springMVC solution for processing.

2 Html code

<form id="myForm">
    <input type="file" id="u_photo" name="u_photo" />
    <input type="button" id="submit-btn" value="上传" />
</form>

3 JQueryUpload

$("#submit-btn").on('click', function() {
    $.ajax({
        url:"/test/upload",
        type:"post",
        data:new FormData($("#myForm").get(0)),
        //十分重要，不能省略
        cache: false,
        processData: false,
        contentType: false,
        success: function () {
            alert("上传成功！");
        }
    });
});

4 JQuery file size verification

File size and corresponding behavior control needs to be handled by yourself as needed. This method is only an example method.

$('#u_photo').on('change', function() {
    var file = this.files[0];
    if (file.size > 1024*1000) {
        alert('文件最大1M！')
    }
});

5 JQuery progress bar

Add xhr to the ajax method to control the upload progress. The progress bar can also use the progress of html5. Use other progress bars. Displaying and hiding the progress bar needs to be handled by yourself. This method only briefly introduces the basic control of the progress bar.

xhr: function() {
    var myXhr = $.ajaxSettings.xhr();
    if (myXhr.upload) {
        myXhr.upload.addEventListener('progress', function(e) {
            if (e.lengthComputable) {
                $('progress').attr({
                    value: e.loaded,
                    max: e.total,
                });
            }
        } , false);
    }
    return myXhr;
}

6 springMVC server

6.1 maven dependency

<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.5</version>
</dependency>
<dependency>
    <groupId>commons-fileupload</groupId>
    <artifactId>commons-fileupload</artifactId>
    <version>1.3.2</version>
</dependency>

6.2 servlet-context.xml

<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver" />

6.3 Controller

sample program does not provide file verification. Corresponding code for storage and processing.

@RequestMapping(value="/test/upload",method = RequestMethod.POST)
@ResponseBody
public String upload(@RequestParam("u_photo") MultipartFile u_photo) {
    System.out.println("u_photo="+u_photo.getSize());
    return "ok";
}

7 Compatibility

IE 10+, Firefox 4.0+, Chrome 7+, Safari 5+ , Opera 12+

8 Recommended reading

If you are not satisfied with the above solution, we recommend the following solution:

JQuery File Uploader

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