文件下载功能的编程实现

通过配置action的Stream各项参数,虽然可以进行文件下载,但是却需要把这些信息硬编码在action中,我们在编写代码时,并不知道用户将会访问的资源名,怎么办?实现方法应该有很多很多种了..看代码吧. 不废话了.

Struts2.xml文件内容

<default-action-ref name="index" />

<result>/jsp/product.jsp</result>

</action>

<param name="inputName">inputStream</param>

</result>

</action>

</package>

</struts>

商品类,Product.java内容

package com.download.domain;

public class Product {

private int id;

private String name;

public Product(){}

public Product(int id,String name){

this.id=id;

this.name=name;

}

public int getId() {

return id;

}

public void setId(int id) {

this.id = id;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

显示所有商品列表,ShowProducts.java内容

package com.download.action;

import java.util.ArrayList;

import java.util.List;

import com.download.domain.Product;

import com.opensymphony.xwork2.ActionSupport;

public class ShowProducts extends ActionSupport {

public List<Product> getProducts(){

List<Product> list=new ArrayList<Product>();

list.add(new Product(1,"电视"));

list.add(new Product(2,"电脑"));

list.add(new Product(3,"影碟机"));

list.add(new Product(4,"游戏机"));

return list;

}

动态获得商品图片,GetImage.java内容

package com.download.action;

import java.io.File;

import java.io.FileInputStream;

import java.io.InputStream;

import javax.servlet.ServletContext;

import javax.servlet.http.HttpServletResponse;

import org.apache.struts2.dispatcher.StreamResult;

import org.apache.struts2.interceptor.ServletResponseAware;

import org.apache.struts2.util.ServletContextAware;

import com.opensymphony.xwork2.ActionContext;

import com.opensymphony.xwork2.ActionSupport;

import com.opensymphony.xwork2.Result;

public class GetImage extends ActionSupport implements ServletContextAware, ServletResponseAware{

private int productId;

public void setProductId(int productId) {

this.productId = productId;

}

private HttpServletResponse httpServletResponse;

private ServletContext servletContext;

@Override

public void setServletResponse(HttpServletResponse httpServletResponse) {

this.httpServletResponse=httpServletResponse;

}

@Override

public void setServletContext(ServletContext servletContext) {

this.servletContext=servletContext;

}

public InputStream getInputStream() throws Exception{

//文件类型

String contentType="image/gif";

//路径

String imageDirectory=servletContext.getRealPath("iamges");

File file=new File(imageDirectory,productId+".gif");

if(!file.exists()){

file=new File(imageDirectory,productId+".jpg");

contentType="image/jpeg";

}

if(!file.exists()){

file=new File(imageDirectory,"noimage.jpg");

contentType="image/jpeg";

}

if(file.exists()){

Result result=ActionContext.getContext().getActionInvocation().getResult();

if(result!=null && result instanceof InputStream){

StreamResult streamResult=(StreamResult)result;

streamResult.setContentType(contentType);

}

return new FileInputStream(file);

}

return null;

}

商品显示页面

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>

<%@ taglib prefix="s" uri="/struts-tags"%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>

<head>

<title>Download2</title>

</head>

<body>

<div>

<table>

<tr>

<td>Pricture</td>

</tr>

<s:iterator value="products" id="product">

<tr>

<td>

<s:url action="getImage" id="url">

<s:param name="productId">

<s:property value="#product.id"/>

</s:param>

</s:url>

<img src="<s:property value="#url"/>" width="100" height="50"/>

</td>

</tr>

</s:iterator>

</table>

<s:debug/>

</div>

</body>

</html>

访问如下:

注意:

启动tomcat的时候,遇到一点问题.看错误信息,检查了半天..结果还是这样,网上找了下.说没有commons-fileupload.jar造成的,但是我有这个jar包啊。。后来把jar包全部删掉,重新在Struts的示例文件里copy了一份,就正常了.错误信息如下:

Unable to load configuration. - action - file:/D:/1Y2/Java%E6%96%B9%E5%90%91/Struts2_LL/.metadata/.me_tcat/webapps/download/WEB-INF/classes/struts.xml:18:63

at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:58)

at org.apache.struts2.dispatcher.Dispatcher.init_PreloadConfiguration(Dispatcher.java:374)

at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:418)

at org.apache.struts2.dispatcher.ng.InitOperations.initDispatcher(InitOperations.java:69)

at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.init(StrutsPrepareAndExecuteFilter.java:51)

at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:275)

at org.apache.catalina.core.ApplicationFilterConfig.setFilterDef(ApplicationFilterConfig.java:397)

at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:108)

at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:3693)

at org.apache.catalina.core.StandardContext.start(StandardContext.java:4340)

at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:791)

at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:771)

at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:525)

at org.apache.catalina.startup.HostConfig.deployDirectory(HostConfig.java:920)

at org.apache.catalina.startup.HostConfig.deployDirectories(HostConfig.java:883)

at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:492)

at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1138)

at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:311)

at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117)

at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1053)

at org.apache.catalina.core.StandardHost.start(StandardHost.java:719)

at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045)

at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443)

at org.apache.catalina.core.StandardService.start(StandardService.java:516)

at org.apache.catalina.core.StandardServer.start(StandardServer.java:710)

at org.apache.catalina.startup.Catalina.start(Catalina.java:566)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)

at java.lang.reflect.Method.invoke(Method.java:597)

at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:288)

at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:413)

Caused by: Action class [com.download.action.DownLoad] not found - action - file:/D:/1Y2/Java%E6%96%B9%E5%90%91/Struts2_LL/.metadata/.me_tcat/webapps/download/WEB-INF/classes/struts.xml:18:63

at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.verifyAction(XmlConfigurationProvider.java:409)

at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.addAction(XmlConfigurationProvider.java:354)

at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.addPackage(XmlConfigurationProvider.java:468)

at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadPackages(XmlConfigurationProvider.java:264)

at org.apache.struts2.config.StrutsXmlConfigurationProvider.loadPackages(StrutsXmlConfigurationProvider.java:111)

at com.opensymphony.xwork2.config.impl.DefaultConfiguration.reloadContainer(DefaultConfiguration.java:193)

at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:55)

... 31 more

2010-9-4 22:50:35 org.apache.catalina.core.StandardContext filterStart

严重: Exception starting filter struts2

Unable to load configuration. - action - file:/D:/1Y2/Java%E6%96%B9%E5%90%91/Struts2_LL/.metadata/.me_tcat/webapps/download/WEB-INF/classes/struts.xml:18:63

at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:431)