java接口下载文件 java提供文件下载接口

需求： 在工程中，放置WORD模板文件供用户下载

功能：页面提供下载链接，用户点击链接后，实现文件下载。

理解：刚开始以为直接用超链接指向文件即可，或用js实现，后来发现都不行。

实现：最后在网上搜了一个实现HTTP文件下载的java类，只要调用如下代码即可。

下面代码放在request经过的地方都可以，如servlet,struts的action或jsp页面。

basePath =  "啊啊啊.doc"; // 我用的是servlet，啊啊啊.doc放在root根目录下
 DownLoadUtil su = new DownLoadUtil();
 su.initialize(request.getSession().getServletContext(), request,
 response);
 su.setContentDisposition(null);
 su.downloadFile(basePath);以下为java下载类代码：
package com.test;


 import java.io.FileInputStream;
 import java.io.IOException;


 import javax.servlet.ServletConfig;
 import javax.servlet.ServletContext;
 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 import javax.servlet.http.HttpSession;
 import javax.servlet.jsp.JspWriter;
 import javax.servlet.jsp.PageContext;


 public class DownLoadUtil {


 protected ServletContext m_application;
 private boolean m_denyPhysicalPath;
 protected HttpServletResponse m_response;
 private String m_contentDisposition;
 protected HttpServletRequest m_request;


 public final void initialize(ServletConfig servletconfig,
 HttpServletRequest httpservletrequest,
 HttpServletResponse httpservletresponse) throws ServletException {
 m_application = servletconfig.getServletContext();
 m_request = httpservletrequest;
 m_response = httpservletresponse;
 }


 public final void initialize(ServletContext context,HttpServletRequest request,HttpServletResponse response)
 throws ServletException {
 m_application = context;
 m_request = (HttpServletRequest) request;
 m_response = (HttpServletResponse) response;
 }


 public final void initialize(ServletContext servletcontext,
 HttpSession httpsession, HttpServletRequest httpservletrequest,
 HttpServletResponse httpservletresponse, JspWriter jspwriter)
 throws ServletException {
 m_application = servletcontext;
 m_request = httpservletrequest;
 m_response = httpservletresponse;
 }


 public void setContentDisposition(String s) {
 m_contentDisposition = s;
 }


 public void downloadFile(String s) throws IOException {
 downloadFile(s, null, null);
 }


 public void downloadFile(String s, String s1) throws IOException {
 downloadFile(s, s1, null);
 }


 public void downloadFile(String s, String s1, String s2) throws IOException {
 downloadFile(s, s1, s2, 65000);
 }


 public void downloadFile(String s, String s1, String s2, int i)
 throws IOException {
 if (s == null) {
 throw new IllegalArgumentException("File '" + s
 + "' not found (1040).");
 }
 if (s.equals(""))
 throw new IllegalArgumentException("File '" + s
 + "' not found (1040).");
 if (!isVirtual(s) && m_denyPhysicalPath)
 throw new SecurityException("Physical path is denied (1035).");
 if (isVirtual(s))
 s = m_application.getRealPath(s);
 java.io.File file = new java.io.File(s);
 FileInputStream fileinputstream = new FileInputStream(file);
 long l = file.length();
 int k = 0;
 byte abyte0[] = new byte[i];
 if (s1 == null)
 m_response.setContentType("application/x-msdownload");
 else if (s1.length() == 0)
 m_response.setContentType("application/x-msdownload");
 else
 m_response.setContentType(s1);
 m_response.setContentLength((int) l);
 m_contentDisposition = m_contentDisposition != null ? m_contentDisposition
 : "attachment;";
 if (s2 == null)
 m_response.setHeader("Content-Disposition", m_contentDisposition
 + " filename=" + toUtf8String(getFileName(s)));
 else if (s2.length() == 0)
 m_response.setHeader("Content-Disposition", m_contentDisposition);
 else
 m_response.setHeader("Content-Disposition", m_contentDisposition
 + " filename=" + toUtf8String(s2));
 while ((long) k < l) {
 int j = fileinputstream.read(abyte0, 0, i);
 k += j;
 m_response.getOutputStream().write(abyte0, 0, j);
 }
 fileinputstream.close();
 }


 private boolean isVirtual(String s) {
 if (m_application.getRealPath(s) != null) {
 java.io.File file = new java.io.File(m_application.getRealPath(s));
 return file.exists();
 } else {
 return false;
 }
 }


 private String getFileName(String s) {
 int i = 0;
 i = s.lastIndexOf(47);
 if (i != -1)
 return s.substring(i + 1, s.length());
 i = s.lastIndexOf(92);
 if (i != -1)
 return s.substring(i + 1, s.length());
 else
 return s;
 }


 public static String toUtf8String(String s) {
 StringBuffer sb = new StringBuffer();
 for (int i = 0; i < s.length(); i++) {
 char c = s.charAt(i);
 if (c >= 0 && c <= 255) {
 sb.append(c);
 } else {
 byte[] b;
 try {
 b = Character.toString(c).getBytes("utf-8");
 } catch (Exception ex) {
 b = new byte[0];
 }
 for (int j = 0; j < b.length; j++) {
 int k = b[j];
 if (k < 0)
 k += 256;
 sb.append("%" + Integer.toHexString(k).toUpperCase());
 }
 }
 }
 return sb.toString();
 }


 }