1、攔截器

定義一個action。.

TestAction.java

package com.zking.study.five;
 
/**
 *  用於測試的action，與普通action沒啥區別
 */
public class TestAction{
 
	public String execute() {
		System.out.println("進入了InterceptorAction的execute方法。");
		return null;
	}
}

定義一個攔截器，實現Interceptor介面，（ com.opensymphony.xwork2.interceptor.Interceptor ）

TestInterceptor.java

package com.zking.study.five;
 
import com.opensymphony.xwork2.ActionInvocation;
import com.opensymphony.xwork2.interceptor.Interceptor;
/**
 *  用於測試的攔截器，實現Interceptor介面
 */
public class TestInterceptor implements Interceptor{
 
	@Override
	public void destroy() {
		System.out.println("TestInterceptor is destroying.");
	}
	@Override
	public void init() {
		System.out.println("TestInterceptor is initing.");
	}
	@Override
	public String intercept(ActionInvocation arg0) throws Exception {
		System.out.println("攔截的類："+arg0.getAction().getClass().getName());
		System.out.println("呼叫的Action是："+arg0.getProxy().getActionName());
		System.out.println("呼叫的方法是："+arg0.getProxy().getMethod());
		arg0.invoke();
		return null;
	}
}
 

 struts中的配置檔案  struts-sy.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE struts PUBLIC
	"-//Apache Software Foundation//DTD Struts Configuration 2.5//EN"
	"http://struts.apache.org/dtds/struts-2.5.dtd">
<struts>
	<package name="sy" extends="base" namespace="/sy">
    <!-- 攔截器定義在package標籤下，於action同級 -->
	<interceptors>
		<interceptor name="testInterceptor" class="com.zking.study.five.TestInterceptor"></interceptor>
	</interceptors>
    <!-- 配置我們之前寫的那個測試action -->
		<action name="testAction" class="com.zking.study.five.TestAction">
            <!-- 將之前定義好的攔截器配置到action裡，（可配置多個） -->
			<interceptor-ref name="testInterceptor"></interceptor-ref>
		</action>
	</package>
</struts>
 

在上面第二段程式碼塊TestInterceptor.java中，destroy方法為攔截器被銷燬時呼叫的方法、init方法為攔截器初始化時呼叫的方法，前面兩個方法都沒什麼好說的，最後一個方法以及它的引數才是重點。

 intercept(ActionInvocation arg0)  ，在這裡就不多解釋了： https://blog.csdn.net/beliefyou8/article/details/51956279

2、檔案上傳、下載
 

在下面的demo中是用到了一個jar包的 commons-io-2.5.jar，使用前需要先將jar包匯入進去，不導jar也行，需自己寫檔案操作的程式碼。

<!-- struts中的s標籤 -->
<s:form action="fileAction_upload" namespace="/sy" method="post" enctype="multipart/form-data">
	<input type="file" name="file">
	<input type="submit">
</s:form>

定義上傳、下載、開啟檔案的類

package com.zking.study.five;
 
import java.io.File;
import java.io.IOException;
 
import org.apache.commons.io.FileUtils;
 
import com.zking.study.four.base.BaseAction;
 
/**
 *  檔案上傳下載
 */
public class FileAction extends BaseAction{
//這是jsp頁面傳遞過來的具體檔案
	private File file;
	//檔名
	private String fileFileName;
	//檔案型別
	private String fileContentType;
	//虛擬路徑
	private String serverDir="/upload";
	
	public File getFile() {
		return file;
	}
 
	public void setFile(File file) {
		this.file = file;
	}
 
	public String getFileFileName() {
		return fileFileName;
	}
 
	public void setFileFileName(String fileFileName) {
		this.fileFileName = fileFileName;
	}
 
	public String getFileContentType() {
		return fileContentType;
	}
 
	public void setFileContentType(String fileContentType) {
		this.fileContentType = fileContentType;
	}
 
	//上傳圖片到tomcat
	public String upload() {
		String realPath = getRealPath(serverDir+"/"+fileFileName);
		try {
			FileUtils.copyFile(file, new File(realPath));
		} catch (IOException e) {
			e.printStackTrace();
		}
		return "success";
	}
	//得到伺服器中的真實路徑
	private String getRealPath(String path) {
		return this.request.getServletContext().getRealPath(path);
	}
	
	//儲存圖片
	public String saveAs() {
		String fileName="stationmaster_img.png";
		String fileType="image/png";
		this.response.setContentType(fileType);
		this.response.setHeader("Content-Disposition","attachment;filename=" + fileName);
		String realPath=getRealPath(serverDir+"/"+fileName);
		try {
            //commons-io-2.5.jar 中的方法，不使用該方法則需自己寫檔案操作的方法。
			FileUtils.copyFile(new File(realPath), response.getOutputStream());
		} catch (IOException e) {
			e.printStackTrace();
		}
		return null;
	}
	//開啟圖片
	public String openAs() {
		String fileName="stationmaster_img.png";
		String fileType="image/png";
		this.response.setContentType(fileType);
		this.response.setHeader("Content-Disposition","filename=" + fileName);
		String realPath=getRealPath(serverDir+"/"+fileName);
		try {
			FileUtils.copyFile(new File(realPath), response.getOutputStream());
		} catch (IOException e) {
			e.printStackTrace();
		}
		return null;
	}
}

BaseAction.java

package com.zking.study.four.base;
 
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
 
import org.apache.struts2.interceptor.ServletRequestAware;
import org.apache.struts2.interceptor.ServletResponseAware;
 
public class BaseAction implements ServletRequestAware, ServletResponseAware{
 
	/**
	 * 為了傳值使用
	 */
	protected HttpServletRequest request;
	protected HttpServletResponse response;
	protected HttpSession session;
	protected ServletContext application;
	
	/**
	 * 為了配置跳轉頁面所用
	 */
	protected final static String SUCCESS="success";
	protected final static String FAIL="fail";
	protected final static String LIST="list";
	protected final static String ADD="add";
	protected final static String PROADD="proAdd";
	protected final static String EDIT="edit";
	protected final static String PROEDIT="proEdit";
	protected final static String DEL="del";
	protected final static String TOLIST="tolist";
	protected final static String DETAIL="detail";
	
	/**
	 * 具體傳值欄位		後端向jsp頁面傳值所用欄位
	 */
	protected Object result;
	protected Object msg;
	protected int code;
	
	
	public Object getResult() {
		return result;
	}
	public Object getMsg() {
		return msg;
	}
	public int getCode() {
		return code;
	}
	@Override
	public void setServletResponse(HttpServletResponse response) {
		// TODO Auto-generated method stub
		this.response=response;
	}
	@Override
	public void setServletRequest(HttpServletRequest request) {
		// TODO Auto-generated method stub
		this.request=request;
	}
}

點選上傳後跳轉的頁面 

<body>
<img src="${pageContext.request.contextPath}/sy/fileAction_openAs.action">
 
<a href="${pageContext.request.contextPath}/sy/fileAction_saveAs.action">點選下載</a>
</body>

struts2配置檔案

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE struts PUBLIC
	"-//Apache Software Foundation//DTD Struts Configuration 2.5//EN"
	"http://struts.apache.org/dtds/struts-2.5.dtd">
<struts>
	<package name="sy" extends="base" namespace="/sy">
		<action name="fileAction_*" class="com.zking.study.five.FileAction" method="{1}">
			<result name="success">/success.jsp</result>
		</action>
	</package>
</struts>

上傳檔案是有兩個概念需要理解的，虛擬路徑與真實路徑的概念？

相對於你所在的開發電腦而言，你自己電腦上有的就是真實路徑，你電腦上沒有的路徑就是虛擬的。