1 file upload

1.1 Implement file upload conditions

1 ) The form submission method must be POST method . (only the content-type attribute)

2 ) There is a file upload form, and the form has a tag for selecting a file with <input type="file"/>

3 ) Set the form to enctype="multipart/form-data" , the submitted data is no longer a key-value pair, but byte data

Please select a file: <input type= "file" name= "img" /><br/>

</form>

1.2 Manually parse the uploaded file

/**

* The information format of the uploaded file

* The first line: the beginning of the file

The second line: the uploaded file header information (including the file name)

Third line: content-type

Fourth line: blank line

Fifth line: start file content

The line after the end of the file content: the end character of the file (the symbol is the same as the start character of the file)

public class UploadDemo1 extends HttpServlet {

public void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

// get entity content data

InputStream in = request.getInputStream();

// Convert to character input stream

BufferedReader br = new BufferedReader(new InputStreamReader(in));

// read the start of the file

String startTag = br.readLine();

// Read the file name: Content-Disposition: form-data; name=" img "; filename="news.txt"

String line = br.readLine();

String fileName = line.substring(line.lastIndexOf("filename=\"")+10, line.lastIndexOf("\"") );

// skip 2 lines

br.readLine();

// read the actual content of the file

String str = null;

BufferedWriter bw = new BufferedWriter(new FileWriter("E:/files/"+fileName));

while((str=br.readLine())!=null){

// Exit the loop when the end of file is read

if((startTag+"--").equals(str)){

break;

}

//把内容写出文件中

bw.write(str);

//写入换行符

bw.newLine();

bw.flush();

}

//关闭

bw.close();

br.close();

}

2 工具实现文件上传

2.1 commons-fileupload组件

是Apache组织旗下的开源的文件上传的组件。使用非常简单易用。

导入commoms-fileuload的jar包：

commons-fileupload-1.2.2.jar 核心包

commons-io-2.1.jar 辅助包

2.2 核心的API

DiskFileItemFactory类：用于创建上传对象，设置文件缓存区大小，设置文件缓存目录。

ServletFileUpload类：用于在Servlet程序中实现文件上传

List<FileItem> list = parseRequest(request): 用于解析请求数据，提取和封装文件信息。

FileItem类：封装一个文件的所有相关的信息。包含文件名称，文件大小，文件类型，文件数据内容。

2.3文件上传的细节

(1) ServletFileUpload类：

setFileSizeMax：设置单个文件的最大容量。（超出抛异常：FileSizeLimitExceededException）

setSizeMax ：设置所有文件的最大容量。（超出抛异常：SizeLimitExceededException）

etProgressListener(new MyProgressListener());注册上传监听器

(2) FileItem类：

①　file.getContentType();//得到文件类型

②　file.isFormField()//判断该FileItem是否是普通文本（除file组件外的其他表单组件）

//得到普通文本控件内容

if(file.isFormField()){

String fieldName = file.getFieldName();

if("info1".equals(fieldName)){

String info1 = file.getString("utf-8");

System.out.println("描述1："+info1);

}

2.4 实现单文件上传

//1.创建DiskFileItemFactory类

/**

* 参数一：表示文件缓存区的大小。如果上传的文件没有超过缓存区大小，则文件不缓存；否则缓存文件，缓存到临时目录。（byte）

* 参数二：表示缓存区的临时目录。

DiskFileItemFactory factory = new DiskFileItemFactory(10*1024,new File("e:/temp/"));

//2.创建ServletFileUpload类

ServletFileUpload upload = new ServletFileUpload(factory);

upload.setHeaderEncoding("utf-8");//通过设置文件头编码格式来解决文件名称中文乱码问题

try {

//3.解析request数据（把每一个文件封装到FileItem对象中，FileItem放入List中）

List<FileItem> list = upload.parseRequest(request);

//取出第一个上传的文件

FileItem file = list.get(0);

//得到文件名(getName())

String fileName = file.getName();

//得到文件大小

long fileSize = file.getSize();

//得到内容类型

String contentType = file.getContentType();

//得到文件数据内容

InputStream in = file.getInputStream();

/**

* 4.把文件数据内容存储到服务器端的硬盘中

FileUtils.copyInputStreamToFile(in, new File("e:/files/"+fileName));

/**

* 5.文件上传完毕，手动清理缓存文件

file.delete();

} catch (FileUploadException e) {

e.printStackTrace();

}

2.5 动态选择多文件上传

<html>

var id = 2;

//添加一行

function addIten(){

var tbodyNode = document.getElementsByTagName("tbody")[0];

var trNode = document.createElement("tr");

trNode.setAttribute("id", id);

var tdNode1 = document.createElement("td");

tdNode1.innerHTML = "请选择文件：";

var tdNode2 = document.createElement("td");

var input1 = document.createElement("input");

input1.setAttribute("type", "file");

input1.setAttribute("name", "file");

var input2 = document.createElement("input");

input2.setAttribute("type", "button");

input2.setAttribute("value", "删除");

input2.setAttribute("onclick", "delItem("+id+")");

tdNode2.appendChild(input1);

tdNode2.appendChild(input2);

trNode.appendChild(tdNode1);

trNode.appendChild(tdNode2);

tbodyNode.appendChild(trNode);

id++;

}

//删除一行（根据tr的id值删除）

function delItem(id){

if(id>1){

var trNode = document.getElementById(id);

var tbodyNode = document.getElementsByTagName("tbody")[0];

tbodyNode.removeChild(trNode);

id--;

}

//提交并且检查file属性

function checkSunbit(){

//检查file属性是否全部填上

var fileList = document.getElementsByName("file");

for(var i=0;i<fileList.length;i++){

//如果为选择file，则其value值为空

if(fileList[i].value==null || fileList[i].value==""){

alert("请选择第"+(i+1)+"个文件");

return false;

}

//提交表单

var form = document.forms['uploadForm'];

form.submit();

}

</script>

</html>

3文件下载

3.1 普通文件下载

使用超链接。缺点：1）暴露文件的路径 2）扩展型和安全性不好

3.2 使用servlet程序下载（推荐）

//得到需要下载的文件

//String path = this.getServletContext().getRealPath("/upload/1.png");

//File file = new File(path);

//FileInputStream in = new FileInputStream(file);

//读取服务器本地的文件

InputStream in = this.getServletContext().getResourceAsStream("/upload/1.png");

/**

* 处理URL编码问题

String fileName = file.getName();

//对文件名进行URl编码

fileName = URLEncoder.encode(fileName, "utf-8");

//判断不同浏览器

String userAgent = request.getHeader("user-agent");

String filefix = null;

if(userAgent.contains("Trident")){

//IE

filefix = "filename="+fileName;

}else{

filefix = "filename*="+fileName;

}

//告诉浏览器以下载方式打开资源

response.setHeader("Content-Disposition", "attachment;"+filefix);

//把本地文件发送给浏览器

byte[] buf = new byte[1024];

int len = 0;

while( (len=in.read(buf))!=-1 ){

response.getOutputStream().write(buf, 0, len);

}