项目实例改编：利用structs2的action 实时显示图片、pdf和其他内容的框架抽取。（转）...

转自：http://www.verydemo.com/demo_c167_i1382.html

针对：预览文件（图片，PDF）文件来源为action中的inputStream

重点：

structs2的action的配置
action的写法和结果类型
resulttype的写法
网页上实时显示

1 structs2的action的配置

　　首先在package的标签中加入自定义的结果类型<result-types>的名字displayResult，以及后面提到的自定义类DisplayFileResult，虽然不配置也不影响用户体验，但 structs默认的结果类型没有直接适合的，例如使用stream会打印结果异常，如果不想异常，就在代码中不要调用inputStream的close方法。

<package name="file" extends="structs-default">   ......<result-types><result-type name="displayResult"class="ssc.net.cn.ecp.portal.bl.file.result.DisplayFileResult" /></result-types>......</package>

在 <result-types>后配置图片资源的action。见 <action name="showImageContent" > ，在成功结果类型的type属性上加上displayResult

<package name="file" extends="structs-default">   ......<result-types><result-type name="displayResult"class="ssc.net.cn.ecp.portal.bl.file.result.DisplayFileResult" /></result-types><action name="showImageContent"class="ssc.net.cn.ecp.portal.bl.file.action.ShowFileContent" method="showImage"><result name="success" type="displayResult"></result><result name="error" /></action><action name="showPdfContent"class="ssc.net.cn.ecp.portal.bl.file.action.ShowFileContent" method="showPdf"><result name="success" type="displayResult"></result><result name="error"/></action>.</package>

2 action的写法和结果类型。

　　此处给出一个框架式的写法，加入最少两个方法getInputStream()和getContentType(),供DisplayFileResult类使用。

import org.apache.struts2.ServletActionContext;
import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionSupport;public class ShowFileContent extends ActionSupport {private InputStream inputStream;public InputStream getInputStream() {return inputStream;}public void setInputStream(InputStream inputStream) {this.inputStream = inputStream;}private String contentType;public String getContentType() {return contentType;}public void setContentType(String contentType) {this.contentType = contentType;}public String showImage() {try  {HttpServletRequest request = (HttpServletRequest) ActionContext.getContext().get(ServletActionContext.HTTP_REQUEST);String filePath = request.getParameter("filepath");this.setInputStream(new java.io.FileInputSteam(filePath));this.setContentType("image/png");}catch  (IOException e) {return ERROR}return SUCCESS;  }public String showPdf()  {try {HttpServletRequest request= (HttpServletRequest) ActionContext.getContext().get(ServletActionContext.HTTP_REQUEST);String filePath = request.getParameter("filepath");this.setInputStream(new java.io.FileInputSteam(filePath));this.setContentType("application/pdf");}catch  (IOException e){return ERROR}return SUCCESS;}｝

3 result type的写法

　　调用response相关方法，把输出流转换为资源方式。在这里，我再老生长谈一句话：一定要切记关闭流，如果不关闭流，在打开过多流后操作系统（Linux）会报类似“too many open files”之类的错误，导致无法访问文件。

package ssc.net.cn.ecp.portal.bl.file.result;import java.io.IOException;import javax.servlet.http.HttpServletResponse;
import org.apache.struts2.ServletActionContext;import com.opensymphony.xwork2.ActionInvocation;
import com.opensymphony.xwork2.Result;public class DisplayFileResult implements Result {private static final long serialVersionUID = 4897546905647587338L;private HttpServletResponse response;ShowFileContent action;public void execute(ActionInvocation invocation) throws Exception {init(invocation);writeResponseOutputStream();}private void init(ActionInvocation invocation) {action = (ShowFileContent) invocation.getAction();response = ServletActionContext.getResponse();response.setContentType(action.getContentType());}private void writeResponseOutputStream() {java.io.InputStream is = action.getInputStream();java.io.BufferedInputStream bi = null;if (is == null) {return;}try {bi = new java.io.BufferedInputStream(is);byte[] bytearray = new byte[1024];int size = 0;while ((size = bi.read(bytearray)) != -1) {response.getOutputStream().write(bytearray, 0, size);}} catch (IOException e) {e.printStackTrace();} finally {try {response.flushBuffer();} catch (IOException e) {e.printStackTrace();}try {bi.close();} catch (IOException e) {e.printStackTrace();}try {is.close();} catch (IOException e) {e.printStackTrace();}}}}