上面的出错提示是Struts 2默认的，大多数情况下，我们都需要自定义和国际化这些信息。通过在全局的国际资源文件中加入“struts.messages.error.content.type.not.allowed=The file you uploaded is not a image”，可以实现以上提及的需求。对此有疑问的朋友可以参考我之前的文章《在Struts 2.0中国际化(i18n)您的应用程序》。
实现之后的出错页面如下图所示：
 |
| 清单13：自定义出错提示页面 |
同样的做法，你可以使用参数“maximumSize”来限制上传文件的大小，它对应的字符资源名为：
“struts.messages.error.file.too.large”。
字符资源“struts.messages.error.uploading”用提示一般的上传出错信息。
多文件上传
与单文件上传相似，Struts 2实现多文件上传也很简单。你可以将多个<s:file />绑定Action的数组或列表。如下例所示。
清单14：多文件上传JSP代码片段
< s:form action ="doMultipleUploadUsingList" method ="POST" enctype ="multipart/form-data" >
< s:file label ="File (1)" name ="upload" />
< s:file label ="File (2)" name ="upload" />
< s:file label ="FIle (3)" name ="upload" />
< s:submit />
</ s:form >
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如果你希望绑定到数组，Action的代码应类似：
清单15：多文件上传数组绑定Action代码片段
private File[] uploads;
private String[] uploadFileNames;
private String[] uploadContentTypes; public File[] getUpload() { return this .uploads; }
public void setUpload(File[] upload) { this .uploads = upload; }
public String[] getUploadFileName() { return this .uploadFileNames; }
public void setUploadFileName(String[] uploadFileName) { this .uploadFileNames = uploadFileName; }
public String[] getUploadContentType() { return this .uploadContentTypes; }
public void setUploadContentType(String[] uploadContentType) { this .uploadContentTypes = uploadContentType; }
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如果你想绑定到列表，则应类似：
清单16：多文件上传列表绑定Action代码片段
private List < File > uploads = new ArrayList < File > ();
private List < String > uploadFileNames = new ArrayList < String > ();
private List < String > uploadContentTypes = new ArrayList < String > (); public List < File > getUpload() {
return this .uploads;
}
public void setUpload(List < File > uploads) {
this .uploads = uploads;
}
public List < String > getUploadFileName() {
return this .uploadFileNames;
}
public void setUploadFileName(List < String > uploadFileNames) {
this .uploadFileNames = uploadFileNames;
}
public List < String > getUploadContentType() {
return this .uploadContentTypes;
}
public void setUploadContentType(List < String > contentTypes) {
this .uploadContentTypes = contentTypes;
}
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总结
在Struts 2中实现文件上传的确是轻而易举，您要做的只是使用<s:file />与Action的属性绑定。这又一次有力地证明了Struts 2的简单易用。
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