seam中另一种上传下载的实现思路

来自：blog.youkuaiyun.com/bq_cui/article/details/3860416

开始：

用'seam create-entity'命令，或用 JBoss Tools ，在项目上单击右键，然后"New -> Seam Entity" ，Entity 名为"Attachment"。我们仅用部分生成代码，只是为了在正确的位置建立相应文件，这样可以不必担心文件位置。

 

下一步，修改 Attachment.java ：

 

[java]  view plain copy

1. import javax.persistence.Basic;  
2. import javax.persistence.Column;  
3. import javax.persistence.Entity;  
4. import javax.persistence.FetchType;  
5. import javax.persistence.GeneratedValue;  
6. import javax.persistence.Id;  
7. import javax.persistence.Lob;  
8.   
9. @Entity  
10. public class Attachment implements java.io.Serializable {  
11.   
12.     @Id  
13.     @GeneratedValue  
14.     private Long id;  
15.     public Long getId() { return this.id; }  
16.     public void setId(Long id) { this.id = id; }  
17.       
18.     private String name;  
19.     public String getName() { return this.name; }  
20.     public void setName(String name) { this.name = name; }  
21.       
22.     private long size;  
23.     public long getSize() { return this.size; }  
24.     public void setSize(long size) { this.size = size; }  
25.       
26.     private String contentType;  
27.     public String getContentType() { return this.contentType; }  
28.     public void setContentType(String contentType) { this.contentType = contentType; }  
29.       
30.     @Lob  
31.     @Column(length = 2147483647)  
32.     @Basic(fetch = FetchType.LAZY)  
33.     private byte[] data;  
34.     public byte[] getData() { return this.data; }  
35.     public void setData(byte[] data) { this.data = data; }  
36.       
37. }  

 

 

现在它已经包含了与s:fileUpload对应的全部字段。

打开 attachment.xhtml ，编辑内容为：

 

[xhtml]  view plain copy

1. <!DOCTYPE composition PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"   
2.                              "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">  
3. <ui:composition xmlns="http://www.w3.org/1999/xhtml"  
4.     xmlns:s="http://jboss.com/products/seam/taglib"  
5.     xmlns:ui="http://java.sun.com/jsf/facelets"  
6.     xmlns:f="http://java.sun.com/jsf/core"  
7.     xmlns:h="http://java.sun.com/jsf/html"  
8.     xmlns:rich="http://richfaces.org/rich" template="layout/template.xhtml">  
9.   
10.     <ui:define name="body">  
11.   
12.         <h:messages globalOnly="true" styleClass="message" />  
13.   
14.         <h:form enctype="multipart/form-data">  
15.   
16.             <rich:panel>  
17.                 <f:facet name="header">Upload Attachment</f:facet>  
18.   
19.                 <s:decorate id="fileUploadDecoration" template="layout/edit.xhtml">  
20.                     <ui:define name="label">Attachment</ui:define>  
21.                     <s:fileUpload id="file"   
22.                               data="#{attachmentHome.instance.data}"  
23.                               contentType="#{attachmentHome.instance.contentType}"  
24.                               fileName="#{attachmentHome.instance.name}"  
25.                               fileSize="#{attachmentHome.instance.size}" />  
26.                 </s:decorate>  
27.                   
28.                 <s:decorate id="nameDecoration" template="layout/display.xhtml">  
29.                     <ui:define name="label">Name</ui:define>  
30.                     <h:outputText value="#{attachmentHome.instance.name}"/>  
31.                 </s:decorate>  
32.                   
33.                 <s:decorate id="contentTypeDecoration" template="layout/display.xhtml">  
34.                     <ui:define name="label">Content Type</ui:define>  
35.                     <h:outputText value="#{attachmentHome.instance.contentType}"/>  
36.                 </s:decorate>  
37.                   
38.                 <s:decorate id="sizeDecoration" template="layout/display.xhtml">  
39.                     <ui:define name="label">Size</ui:define>  
40.                     <h:outputText value="#{attachmentHome.instance.size}"/>  
41.                 </s:decorate>  
42.                   
43.                 <div style="clear: both" mce_style="clear: both" />  
44.             </rich:panel>  
45.               
46.             <div class="actionButtons">  
47.                 <h:commandButton value="Upload"   
48.                          action="#{attachmentHome.persist}"    
49.                          rendered="#{!attachmentHome.managed}"/>  
50.                 <h:commandButton value="Delete"   
51.                          action="#{attachmentHome.remove}"  
52.                          immediate="true"    
53.                          rendered="#{attachmentHome.managed}">  
54.                     <s:conversationPropagation type="end" />  
55.                 </h:commandButton>  
56.                 <s:button propagation="end"   
57.                           id="done"   
58.                           value="Done"  
59.                           view="/attachmentList.xhtml"/>  
60.             </div>  
61.   
62.         </h:form>  
63.   
64.     </ui:define>  
65.   
66. </ui:composition>  

 

 

以上代码与 CRUD 页面的主要区别是，字段是输出文本而非输入，因为字段值由 s:fileUpload component 自动确定。这里的代码你可以随便修改。

 

继续修改 attachmentList.xhtml ，使其可以显示上传文件的属性，并且允许下载：

[xhtml]  view plain copy

1. <!DOCTYPE composition PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"   
2.                              "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">  
3. <ui:composition xmlns="http://www.w3.org/1999/xhtml"  
4.                 xmlns:s="http://jboss.com/products/seam/taglib"  
5.                 xmlns:ui="http://java.sun.com/jsf/facelets"  
6.                 xmlns:f="http://java.sun.com/jsf/core"  
7.                 xmlns:h="http://java.sun.com/jsf/html"  
8.                 xmlns:rich="http://richfaces.org/rich"  
9.                 template="layout/template.xhtml">  
10.                          
11.     <ui:define name="body">  
12.           
13.         <h:messages globalOnly="true" styleClass="message"/>  
14.           
15.         <rich:panel>  
16.             <f:facet name="header">Files Uploaded</f:facet>  
17.               
18.             <div class="results">  
19.               
20.                 <h:outputText value="No files exists" rendered="#{empty attachmentList.resultList}"/>  
21.                          
22.                 <rich:dataTable id="attachmentList"   
23.                              var="attachment"  
24.                              value="#{attachmentList.resultList}"   
25.                              rendered="#{not empty attachmentList.resultList}">  
26.                     <rich:column>  
27.                         <f:facet name="header">File Name</f:facet>  
28.                         <s:link value="#{attachment.name}" view="/attachment.xhtml">  
29.                             <f:param name="attachmentId" value="#{attachment.id}" />  
30.                         </s:link>  
31.                     </rich:column>  
32.                     <rich:column>  
33.                         <f:facet name="header">Content Type</f:facet>  
34.                         #{attachment.contentType}  
35.                     </rich:column>  
36.                     <rich:column>  
37.                         <f:facet name="header">Size(bytes)</f:facet>  
38.                         #{attachment.size}  
39.                     </rich:column>  
40.                     <rich:column>  
41.                         <f:facet name="header">Action</f:facet>  
42.                         <s:link value="Download" action="#{downloadAttachment.download}">  
43.                             <f:param name="attachmentId" value="${attachment.id}" />  
44.                         </s:link>  
45.                     </rich:column>  
46.                 </rich:dataTable>  
47.                   
48.             </div>  
49.               
50.         </rich:panel>  
51.           
52.         <div class="actionButtons">  
53.             <s:button id="done"   
54.                    value="Create attachment"  
55.                     view="/attachment.xhtml"/>               
56.         </div>  
57.           
58.     </ui:define>  
59.   
60. </ui:composition>  

 

 

这里有一个名为 downloadAttachment 的Component，引用了我们还没创建的内容，所以，我们先来建立它。你可以用EJB3 或者 Seam pojo，下面的工作好简单，我们继续。DownloadAttachment 组件是本文的核心，所以要注意了：

 

 

[java]  view plain copy

1. @Name("downloadAttachment")  
2. public class DownloadAttachment {  
3.       
4.     @Logger  
5.     private Log log;  
6.       
7.     @In  
8.     private EntityManager entityManager;  
9.       
10.     @In(value="#{facesContext.externalContext}")  
11.     private ExternalContext extCtx;  
12.       
13.     @In(value="#{facesContext}")  
14.     FacesContext facesContext;  
15.       
16.     @RequestParameter  
17.     private Long attachmentId;  
18.       
19.     public String download() {  
20.         Attachment attachment = entityManager.find(Attachment.class, attachmentId);  
21.         HttpServletResponse response = (HttpServletResponse)extCtx.getResponse();  
22.         response.setContentType(attachment.getContentType());  
23.                 response.addHeader("Content-disposition", "attachment; filename=/"" + attachment.getName() +"/"");  
24.         try {  
25.             ServletOutputStream os = response.getOutputStream();  
26.             os.write(attachment.getData());  
27.             os.flush();  
28.             os.close();  
29.             facesContext.responseComplete();  
30.         } catch(Exception e) {  
31.             log.error("/nFailure : " + e.toString() + "/n");  
32.         }  
33.   
34.         return null;  
35.     }  
36. }  

为圆满完成任务，这里展示AttachmentHome.java 和 AttachmentList.java代码：

 

 

[java]  view plain copy

1. import org.jboss.seam.annotations.Name;  
2. import org.jboss.seam.framework.EntityQuery;  
3.   
4. @Name("attachmentList")  
5. public class AttachmentList extends EntityQuery  
6. {  
7.     @Override  
8.     public String getEjbql()   
9.     {   
10.         return "select attachment from Attachment attachment";  
11.     }  
12. }  

 

[java]  view plain copy

1. import org.jboss.seam.annotations.Name;  
2. import org.jboss.seam.annotations.Begin;  
3. import org.jboss.seam.annotations.web.RequestParameter;  
4. import org.jboss.seam.framework.EntityHome;  
5.   
6. import org.domain.knowledgebase.entity.Attachment;  
7.   
8. @Name("attachmentHome")  
9. public class AttachmentHome extends EntityHome<Attachment> {  
10.   
11.     @RequestParameter   
12.     Long attachmentId;  
13.       
14.     @Override  
15.     public Object getId() {   
16.         if (attachmentId==null) {  
17.             return super.getId();  
18.         } else {  
19.             return attachmentId;  
20.         }  
21.     }  
22.       
23.     @Override @Begin  
24.     public void create() {  
25.         super.create();  
26.     }  
27.       
28. }  

 

 

剩下的事情就是定义出错处理以及在components.xml文件中multipart filter。

在pages.xml中增加：

[xhtml]  view plain copy

1. <exception class="org.jboss.seam.web.FileUploadException">  
2.   <redirect view-id="/error.xhtml">  
3.     <message>#{org.jboss.seam.handledException.message}</message>  
4.   </redirect>  
5. </exception>  

 

components.xml中增加:

 

[xhtml]  view plain copy

1. xmlns:web="http://jboss.com/products/seam/web"  
2. ...  
3. http://jboss.com/products/seam/web http://jboss.com/products/seam/web-2.0.xsd  
4. ...  
5. <web:multipart-filter create-temp-files="true"  
6.                       max-request-size="1000000"   
7.                       url-pattern="*.seam" />  

 

可以将以上内容结合到你自己的web程序。