解决spring mvc 上传报错，Field [] isn't an enum value，Failed to convert value of type 'java.lang.String[]' to required type '

没有选择附件，但是点击上传按钮的时候会报错。

之前不选择文件，直接上传空文件是可以的，后来不知道改了什么就不行了。

错误信息：

2014-03-14 17:32:40 [http-8080-1] TRACE org.springframework.beans.TypeConverterDelegate - Field [] isn't an enum value
java.lang.NoSuchFieldException: 
    at java.lang.Class.getField(Unknown Source)
    at org.springframework.beans.TypeConverterDelegate.attemptToConvertStringToEnum(TypeConverterDelegate.java:296)
    at org.springframework.beans.TypeConverterDelegate.convertIfNecessary(TypeConverterDelegate.java:223)
    at org.springframework.beans.TypeConverterDelegate.convertIfNecessary(TypeConverterDelegate.java:111)
    at org.springframework.beans.TypeConverterDelegate.convertToTypedArray(TypeConverterDelegate.java:461)
    省略一部分…………
    at java.lang.Thread.run(Unknown Source)
2014-03-14 17:32:40 [http-8080-1] TRACE org.springframework.web.method.HandlerMethod - Error resolving argument [2] [type=[Lorg.springframework.web.multipart.MultipartFile;]
HandlerMethod details: 
Controller [com.cvicin.ssm.sys.fileUpload.FileUploadClass]
Method [public java.lang.String com.cvicin.ssm.sys.fileUpload.FileUploadClass.hotProductFinance_fileUpload(java.lang.String,java.lang.String,org.springframework.web.multipart.MultipartFile[],javax.servlet.http.HttpServletRequest)]

org.springframework.beans.ConversionNotSupportedException: Failed to convert value of type 'java.lang.String[]' to required type 'org.springframework.web.multipart.MultipartFile[]'; nested exception is java.lang.IllegalStateException: Cannot convert value of type [java.lang.String] to required type [org.springframework.web.multipart.MultipartFile]: no matching editors or conversion strategy found
    at org.springframework.beans.SimpleTypeConverter.convertIfNecessary(SimpleTypeConverter.java:58)
    at org.springframework.validation.DataBinder.convertIfNecessary(DataBinder.java:553)
    at org.springframework.web.method.annotation.AbstractNamedValueMethodArgumentResolver.resolveArgument(AbstractNamedValueMethodArgumentResolver.java:97)
    at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:75)
    at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:162)
    省略一部分…………
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
    at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.IllegalStateException: Cannot convert value of type [java.lang.String] to required type [org.springframework.web.multipart.MultipartFile]: no matching editors or conversion strategy found
    at org.springframework.beans.TypeConverterDelegate.convertIfNecessary(TypeConverterDelegate.java:247)
    at org.springframework.beans.TypeConverterDelegate.convertIfNecessary(TypeConverterDelegate.java:111)
    at org.springframework.beans.TypeConverterDelegate.convertToTypedArray(TypeConverterDelegate.java:461)
    at org.springframework.beans.TypeConverterDelegate.convertIfNecessary(TypeConverterDelegate.java:178)
    at org.springframework.beans.TypeConverterDelegate.convertIfNecessary(TypeConverterDelegate.java:93)
    at org.springframework.beans.SimpleTypeConverter.convertIfNecessary(SimpleTypeConverter.java:49)
    ... 46 more

解决办法：在上传之前判断有没有附件，没有的话就不执行了上传事件了。

页面代码：

        <form id="saveFile" method="post" enctype="multipart/form-data">    
            <div>上传新的附件:</div>    
            <div>
                <input type="file" name="file" />
                <input type="file" name="file" />
                <input type="file" name="file" />
                <input type="file" name="file" />
                <input type="file" name="file" />
            </div>        
        </form>    

js代码：

var fileFlag = false; 
$("input[name=file]").each(function(){ 
    if($(this).val()!="") { 
        fileFlag = true; 
        return false; 
    } 
}); 
if(fileFlag) { 
    var url = "${pageContext.request.contextPath}/fileUpload/fileUpload";
    $("#saveFile").ajaxSubmit({//执行上传
        url:url,
        success:function(msg){                                       
        //                  
        }
    });                               
}

其实就是jquery选择器，遍历name = file是不是空值。

记下了，省的以后忘了。。。 o(╯□╰)o