使用Response下载文件,servlet中的文件下载是通过流来实现的
我在webRoot文件夹下新建了一个文件夹from,里边放了一张图片,这里就以下载这张图片为例:download.jsp很简单,只有一个a标签.
DownloadAction如下:
package com.wang.action; import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream; import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; import org.apache.struts2.ServletActionContext; import com.opensymphony.xwork2.Action; public class DownloadAction { public String execute() throws IOException{
//获取response和request
HttpServletRequest request=ServletActionContext.getRequest();
HttpServletResponse response=ServletActionContext.getResponse();
//获取要下载的文件夹路径
String path=request.getRealPath("/from");
File file=new File(path,"IMG_0968.jpg");
response.setContentLength((int)file.length());
response.setCharacterEncoding("utf-8");
//此contenttype意思是不知道文件类型,使用二进制流的方式传输
response.setContentType("application/octet-stream");
//注意,filename=后面的内容不加引号,我第一次加了引号,结果出错
response.setHeader("Content-Disposition", "attachment;filename=IMG_0968.jpg"); InputStream is=new FileInputStream(file);
//通过response获得输出流
OutputStream os=response.getOutputStream();
byte[] b=new byte[1024];
int len=0;
while((len=is.read(b))!=-1){
os.write(b, 0, len);
}
is.close();
os.close();
System.out.println("success download");
//注意:这里返回的是null
return null;
}
}
DownloadAction
这是使用servlet的reqsponse下载文件的方式,注意在action中,返回值是null,配置文件中不需要result标签,download.jsp和struts.xml省略.
使用Struts2的StreamResult进行文件下载.
webRoot文件夹下新建了一个文件夹from,里边放了两张图片分别是IMG_0968.jpg和IMG_0975.jpg.以下载这两张图片为例:
downLoad.jsp页面:
<body>
<a href="streamDownload.action?fileName=IMG_0968.jpg">流的方式下载第一张图片</a><br>
<a href="streamDownload.action?fileName=IMG_0975.jpg">流的方式下载第二张图片</a> </body>
StreamDownloadAction页面:
package com.wang.action; import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream; import javax.servlet.http.HttpServletRequest; import org.apache.struts2.ServletActionContext; import com.opensymphony.xwork2.ActionSupport; public class StreamDownload extends ActionSupport{ private String fileName;
@Override
public String execute() throws Exception {
return SUCCESS;
} public InputStream getInputStream() throws IOException{ HttpServletRequest request = ServletActionContext.getRequest();
String path=request.getRealPath("/from");
InputStream is=new FileInputStream(new File(path,fileName));
return is;
} public String getFileName() {
return fileName;
} public void setFileName(String fileName) {
this.fileName = fileName;
} }
StreamDownloadAction
struts.xml页面:
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 2.1//EN" "http://struts.apache.org/dtds/struts-2.1.dtd">
<struts> <package name="default" namespace="/" extends="struts-default">
<action name="streamDownload" class="com.wang.action.StreamDownload">
<result type="stream">
<!-- inputName默认就是InputStream,可以省略,也可以自己修改,如改成aaa,
则Action里的方法也要改成public InputStream getAaa() -->
<param name="inputName">InputStream</param>
<param name="contentDisposition">attachment;fileName=${fileName}</param>
</result>
</action>
</package>
</struts>