文件上传

首先写一个文件上传的页面

jsp页面:

<body>
    <form action="${ pageContext.request.contextPath }/UploadServlet" method="post" enctype="multipart/form-data">
    <table border="1" width="600">
        <tr>
            <td>文件描述</td>
            <td><input type="text" name="filedesc"></td>
        </tr>
        <tr>
            <td>文件上传</td>
            <td><input type="file" name="upload"></td>
        </tr>
        <tr>
            <td colspan="2"><input type="submit" value="上传"></td>
        </tr>
    </table>
</form>
</body>

在写servlet前解决文件重名问题
使用UUID作为随机的文件名

public class UUIDUtils {

    public static String getUUID(){
        return UUID.randomUUID().toString().replace("-", "");
    }
    
    public static String getUUIDFileName(String fileName){
        return UUID.randomUUID().toString().replace("-", "")+"_"+fileName;
    }
}

解决一个目录下存放的文件过多的问题

public class UploadUtils {

    public static String getPath(String uuidFileName){
        // 使用唯一文件名.hashCode();
        int code1 = uuidFileName.hashCode();
        int d1 = code1 & 0xf; // 获得到1级目录.
        int code2 = code1 >>> 4;
        int d2 = code2 & 0xf; // 获得到2级目录.
        return "/"+d1+"/"+d2;
    }
}

此处的servlet是用的servlet3.0

/**
 * 文件上传的Servlet
 */
@WebServlet("/UploadServlet")
@MultipartConfig
public class UploadServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 接收普通数据:
        request.setCharacterEncoding("UTF-8");
        String filedesc = request.getParameter("filedesc");
        System.out.println("文件描述"+filedesc);
        // 接收文件:
        Part part = request.getPart("upload");
        
        long size = part.getSize();// 获得文件大小:
        System.out.println("文件大小:"+size);
        String name = part.getName();
        System.out.println("文件表单中的name属性的名称"+name);
        // 获得文件名:
        String header = part.getHeader("Content-Disposition");
        int idx = header.lastIndexOf("filename="");
        String fileName = header.substring(idx+10, header.length()-1);
        System.out.println("文件名:"+fileName);
        // 获得文件内容:
        InputStream is = part.getInputStream();
        // 获得upload的路径:
        String path = this.getServletContext().getRealPath("/upload");
        // 获得文件的唯一文件名:
        String uuidFileName = UUIDUtils.getUUIDFileName(fileName);
        String realPath = path+UploadUtils.getPath(uuidFileName);
        File file = new File(realPath);
        if(!file.exists()){
            file.mkdirs();
        }
        OutputStream os = new FileOutputStream(realPath+"/"+uuidFileName);
        byte[] b = new byte[1024];
        int len = 0;
        while((len = is.read(b))!=-1){
            os.write(b, 0, len);
        }
        is.close();
        os.close();
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

}