JavaBean 中：
private File[] pic;
private String[] picContentType;
private String [] picFileName;
setter getter
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Action中：
JavaBean javaBean
setter getter
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JSP中：
<form action="aaaa" method="post" enctype="multipart/form-data">
<s:file name="javaBean.pic" />
<s:file name="javaBean.pic" />
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约定：xxx，xxxContentType，xxxFileName