七、Struts2之文件上传与下载

 

一、Struts2文件上传

 

Struts2的文件上传实现非常简单,只需要简单几步就可完成;

注意:

(1)文件上传的struts2标签为:<s:file name="" label="上传"/>

(2)文件上传的前提是表单属性method="post" enctype="multipart/form-data";

(3)web应用中必须包含common-fileupload.jar和common-io.jar,因为struts2默认上传解析器使用的是jakarta;

(4)可以在struts.xml中配置最大允许上传的文件大小:<constant name="struts.multipart.maxSize" value="....."/>,默认为2M;

 

1.普通文件上传

 

实现规则:

(1)在JSP中设定表单控件<s:file name="upload" label="上传"/>

(2)在Action中定义属性:

private File upload;        //包含文件内容

private String uploadFileName;    //上传文件的名称;

private String uploadContentType;    //上传文件的MIME类型;

这些属性都会随着文件的上传自动赋值;

(3)在execute()中完成写入磁盘功能;

 

代码示例:

 

Upload01Action.java

 

package org.upload.action;



import java.io.File;

import java.io.FileInputStream;

import java.io.FileOutputStream;



import org.apache.struts2.ServletActionContext;



import com.opensymphony.xwork2.ActionSupport;



public class Upload01Action extends ActionSupport {

	private File upload;

	private String uploadFileName;

	private String uploadContentType;

	private String name;

	public String execute()throws Exception{

		String path = ServletActionContext.getServletContext().getRealPath("/WEB-INF/upload");

		String filename = path+File.separator+name;

		FileInputStream in = new FileInputStream(upload);

		FileOutputStream out = new FileOutputStream(filename);

		byte[]b = new byte[1024];

		int len = 0;

		while((len=in.read(b))>0){

			out.write(b,0,len);

		}

		out.close();

		return SUCCESS;

	}



	public File getUpload() {

		return upload;

	}



	public void setUpload(File upload) {

		this.upload = upload;

	}



	public String getUploadFileName() {

		return uploadFileName;

	}



	public void setUploadFileName(String uploadFileName) {

		this.uploadFileName = uploadFileName;

	}



	public String getUploadContentType() {

		return uploadContentType;

	}



	public void setUploadContentType(String uploadContentType) {

		this.uploadContentType = uploadContentType;

	}



	public String getName() {

		return name;

	}



	public void setName(String name) {

		this.name = name;

	}

	

	

}

 

struts.xml

 

<?xml version="1.0" encoding="UTF-8" ?>

<!DOCTYPE struts PUBLIC

    "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"

    "http://struts.apache.org/dtds/struts-2.0.dtd">



<struts>

	<constant name="struts.devMode" value="true" />

	<constant name="struts.custom.i18n.resources" value="message"></constant>

	<package name="default" namespace="/"  extends="struts-default">

		<action name="upload0*" class="org.upload.action.Upload0{1}Action">

			<param name="name">1.jpg</param>

			<result>/{1}.jsp</result>

		</action>

	</package>

</struts>


1.jsp

 

<%@ 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>My JSP '1.jsp' starting page</title>

  </head>

  

  <body> 

   	<s:form action="upload01" method="post" enctype="multipart/form-data">

   		<s:file name="upload" label="上传"></s:file>

   		<s:submit value="上传"></s:submit>

   	</s:form>

  </body>

</html>


 

2.利用拦截器进行过滤

 

手动实现过滤的方式非常简单,就是利用输入校验的方式进行过滤,即在validate()中进行过滤;

而这里要讲的拦截器方式是很好的方式,只需要在配置文件中配置,灵活性很好,能够限制文件的类型、文件的大小;如果上传的文件不符合要求,则返回input逻辑视图;

 

配置拦截器步骤:

 

(1)文件上传的拦截器为fileUpload;

(2)需要给定参数allowedTypes、maximumSize;

(3)在fileUpload拦截器后,需要添加<interceptor-ref name="defaultStack"/>

 

代码示例:

 

由于通过拦截器进行过滤只需要配置struts.xml,因此这里只给出struts.xml的配置

 

<?xml version="1.0" encoding="UTF-8" ?>

<!DOCTYPE struts PUBLIC

    "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"

    "http://struts.apache.org/dtds/struts-2.0.dtd">



<struts>

	<constant name="struts.devMode" value="true" />

	<constant name="struts.custom.i18n.resources" value="message"></constant>

	<package name="default" namespace="/"  extends="struts-default">

		<action name="upload0*" class="org.upload.action.Upload0{1}Action">

			<interceptor-ref name="fileUpload">

				<param name="allowedTypes">image/jpeg,image/gif</param>

				<param name="maximumSize">1024*1024</param>

			</interceptor-ref>

			<interceptor-ref name="defaultStack"></interceptor-ref>

			<param name="name">1.jpg</param>

			<result>/{1}.jsp</result>

			<result name="input">/{1}.jsp</result>

		</action>

	</package>

</struts>


 

我们还需要配置文件上传失败后的错误提示信息,我们需要在全局国际化资源文件中配置:

 

struts.messages.error.content.type.not.allowed=文件类型不匹配



struts.messages.error.file.too.large=文件太大




 

 

二、Struts2文件下载

 

我们在学习Servlet和HTTP协议时已经可以实现文件下载,即写content-disposition头即可,struts2的实现原理也是这个,但是提供了更好的封装性;

struts2的stream结果类型专门用于实现文件下载;

(1)struts.xml中配置stream结果类型,并配置contentType、contentDisposition、bufferSize参数即可,模板:

<action name="download" class="">

	<result type="stream" name="success">

		<param name="contentType"></param>

		<param name="contentDisposition">attachment;filename=""</param>

		<param name="bufferSize">4096</param>

	</result>

</action>


(2)在Action中创建public InputStream getInputStream()throws Exception;方法,此方法用于获得下载文件的输入流;

 

DownloadAction.java

 

package org.download.action;



import java.io.InputStream;



import org.apache.struts2.ServletActionContext;



import com.opensymphony.xwork2.ActionSupport;



public class DownloadAction extends ActionSupport {

	public InputStream getInputStream()throws Exception{

		

		return ServletActionContext.getServletContext().getResourceAsStream("/WEB-INF/upload/1.jpg");

		

	}

	public String execute()throws Exception{

		return SUCCESS;

	}

}


struts.xml

 

<action name="download" class="org.download.action.DownloadAction">

			<result type="stream" name="success">

				<param name="contentType">image/jpeg</param>

				<param name="contentDisposition">attachment;filename="1.jpg"</param>

				<param name="bufferSize">4096</param>

			</result>

		</action>


 

就可以完成下载;

 


 

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