seam上传与下载（1）

 以下文章展示了如何在seam中上传下载附件。

 

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 ：

 import javax.persistence.Basic;import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.FetchType;import javax.persistence.GeneratedValue;import javax.persistence.Id;import javax.persistence.Lob;@Entitypublic class Attachment implements java.io.Serializable {@Id@GeneratedValueprivate Long id;public Long getId() { return this.id; }public void setId(Long id) { this.id = id; }private String name;public String getName() { return this.name;}public void setName(String name) { this.name = name; }private long size;public long getSize() { return this.size; }public void setSize(long size) { this.size = size; }private String contentType;public String getContentType() { return this.contentType; }public void setContentType(String contentType) { this.contentType = contentType; }@Lob@Column(length = 2147483647)@Basic(fetch = FetchType.LAZY)private byte[] data;public byte[] getData() { return this.data; }public void setData(byte[] data) { this.data = data; }}

 

 

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：

 

<!DOCTYPE composition PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><ui:composition xmlns="http://www.w3.org/1999/xhtml"xmlns:s="http://jboss.com/products/seam/taglib"xmlns:ui="http://java.sun.com/jsf/facelets"xmlns:f="http://java.sun.com/jsf/core"xmlns:h="http://java.sun.com/jsf/html"xmlns:rich="http://richfaces.org/rich" template="layout/template.xhtml"><ui:define name="body"><h:messages globalOnly="true" styleClass="message" /><h:form enctype="multipart/form-data"><rich:panel><f:facet name="header">Upload Attachment</f:facet><s:decorate id="fileUploadDecoration" template="layout/edit.xhtml"><ui:define name="label">Attachment</ui:define><s:fileUpload id="file" data="#{attachmentHome.instance.data}" contentType="#{attachmentHome.instance.contentType}" fileName="#{attachmentHome.instance.name}" fileSize="#{attachmentHome.instance.size}" /></s:decorate><s:decorate id="nameDecoration" template="layout/display.xhtml"><ui:define name="label">Name</ui:define><h:outputText value="#{attachmentHome.instance.name}"/></s:decorate><s:decorate id="contentTypeDecoration" template="layout/display.xhtml"><ui:define name="label">Content Type</ui:define><h:outputText value="#{attachmentHome.instance.contentType}"/></s:decorate><s:decorate id="sizeDecoration" template="layout/display.xhtml"><ui:define name="label">Size</ui:define><h:outputText value="#{attachmentHome.instance.size}"/></s:decorate><div style="clear: both" mce_style="clear: both" /></rich:panel><div class="actionButtons"><h:commandButton value="Upload" action="#{attachmentHome.persist}" rendered="#{!attachmentHome.managed}"/><h:commandButton value="Delete" action="#{attachmentHome.remove}" immediate="true" rendered="#{attachmentHome.managed}"><s:conversationPropagation type="end" /></h:commandButton><s:button propagation="end" id="done" value="Done" view="/attachmentList.xhtml"/></div></h:form></ui:define></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：

<!DOCTYPE composition PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><ui:composition xmlns="http://www.w3.org/1999/xhtml" xmlns:s="http://jboss.com/products/seam/taglib" xmlns:ui="http://java.sun.com/jsf/facelets" xmlns:f="http://java.sun.com/jsf/core" xmlns:h="http://java.sun.com/jsf/html" xmlns:rich="http://richfaces.org/rich" template="layout/template.xhtml"> <ui:define name="body"> <h:messages globalOnly="true" styleClass="message"/> <rich:panel> <f:facet name="header">Files Uploaded</f:facet> <div class="results"> <h:outputText value="No files exists" rendered="#{empty attachmentList.resultList}"/> <rich:dataTable id="attachmentList" var="attachment" value="#{attachmentList.resultList}" rendered="#{not empty attachmentList.resultList}"> <rich:column> <f:facet name="header">File Name</f:facet> <s:link value="#{attachment.name}" view="/attachment.xhtml"> <f:param name="attachmentId" value="#{attachment.id}" /> </s:link> </rich:column> <rich:column> <f:facet name="header">Content Type</f:facet> #{attachment.contentType} </rich:column> <rich:column> <f:facet name="header">Size(bytes)</f:facet> #{attachment.size} </rich:column> <rich:column> <f:facet name="header">Action</f:facet> <s:link value="Download" action="#{downloadAttachment.download}"> <f:param name="attachmentId" value="${attachment.id}" /> </s:link> </rich:column> </rich:dataTable> </div> </rich:panel> <div class="actionButtons"> <s:button id="done" value="Create attachment" view="/attachment.xhtml"/> </div> </ui:define></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：

 

 @Name("downloadAttachment")public class DownloadAttachment {@Loggerprivate Log log;@Inprivate EntityManager entityManager;@In(value="#{facesContext.externalContext}")private ExternalContext extCtx;@In(value="#{facesContext}")FacesContext facesContext;@RequestParameterprivate Long attachmentId;public String download() {Attachment attachment = entityManager.find(Attachment.class, attachmentId);HttpServletResponse response = (HttpServletResponse)extCtx.getResponse();response.setContentType(attachment.getContentType()); response.addHeader("Content-disposition", "attachment; filename=/"" + attachment.getName() +"/"");try {ServletOutputStream os = response.getOutputStream();os.write(attachment.getData());os.flush();os.close();facesContext.responseComplete();} catch(Exception e) {log.error("/nFailure : " + e.toString() + "/n");}return null;}}