jsp下载文件方法
java.lang.IllegalStateException: getOutputStream() has already been called for this
写的jsp下载文件是这样的：
所要下载的文档在工程的webroot的pdfDoc文件，从上个网页传递的值是file，
注意：1、url传递中文值时用的是ISO8859_1格式，所以获取编码后需要转化为utf-8
2、在jsp中使用File类，如果使用tomcat的话，默认的相对路径是tomcat下的bin文件夹，所以需要使用到绝对路径，这里使用String path1=request. getRealPath( "/");获取jsp的绝对路径
<%@ page language= "java" import= "java.util.*" pageEncoding = "utf-8"%><%@ page language ="java" import= "java.io.*,java.net.*"%><%
String path = request.getContextPath();
String basePath = request.getScheme()+"://" +request.getServerName()+ ":"+request.getServerPort()+path+ "/" ;
%><% //获得JSP页面的路径
String path1=request. getRealPath( "/");
System.out.println(path1);
response.setContentType( "text/html" );
javax.servlet.ServletOutputStream ou = response.getOutputStream();
String filepath = "pdfDoc/" ;
String filename = new String(request.getParameter("file" )
.getBytes( "ISO8859_1" ), "utf-8" ).toString();
System.out.println( "DownloadFile filepath:" + filepath);
System.out.println( "DownloadFile filename:" + filename);
//java.io.File file1 = new java.io.File("t.txt");
//System.out.println(java.io.File.separator);
java.io.File file = new java.io.File(path1+filepath + filename);
if (!file.exists()) {
System.out.println(file.getAbsolutePath() + " 文件不存在!" );
return ;
}
// 读取文件流
// 下载文件
// 设置响应头和下载保存的文件名
if (filename != null && filename.length() > 0) {
response.setContentType( "application/x-msdownload" );
response.setHeader(
"Content-Disposition" ,
"attachment; filename="
+ new String(filename.getBytes("utf-8" ),
"iso8859-1" ) + "" );
java.io.FileInputStream fileInputStream = null ;
OutputStream output = null ;
try {
fileInputStream = new java.io.FileInputStream(file);
output = response.getOutputStream();
if (fileInputStream != null) {
int filelen = fileInputStream.available();
//文件太大时内存不能一次读出,要循环
byte a[] = new byte[1024];
int i = 0;
while ((i = fileInputStream.read(a)) > 0) {
ou.write(a, 0, i);
}
output.flush();
}
} catch (Exception e) {
System.out.println( "error" );
e.printStackTrace();
} finally {
if (fileInputStream != null) {
fileInputStream.close();
}
if (output != null) {
output.close();
}
}
return ;
} %><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
< html>
<head >
</head >
<body >
</body >
</ html>
刚开始时能够下载，但是总是异常：java.lang.IllegalStateException: getOutputStream() has already been called for this
后来看了一篇文章说：<%%>和html接触的地方不要有空格说明在如下：（网址是http://www.360doc.com/content/06/0123/16/677_61900.shtml）
