文件上传进行封装

BaseServlet.java
if(isMultipart){ //如果是上传文件
				request = new MultipartRequestWrapper(request);
			}

MultipartRequestWrapper.java
package cn.com.leadfar.cms.backend.view;

import java.io.FileOutputStream;
import java.io.InputStream;
import java.util.Arrays;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

import org.apache.commons.fileupload.FileItemIterator;
import org.apache.commons.fileupload.FileItemStream;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import org.apache.commons.fileupload.util.Streams;
import org.apache.commons.io.FilenameUtils;

import cn.com.leadfar.cms.backend.model.Attachment;

public class MultipartRequestWrapper extends HttpServletRequestWrapper {

	private Map allParams;
	
	public MultipartRequestWrapper(HttpServletRequest request) {
		super(request);
		
		//首先判断是否multipart编码类型
		//如果是multipart编码类型，就逐个从request中取出各个表单域
		//如果表单域是普通的表单域，则将它的值取出，放到allParams中
		//如果表单域是文件，则
		//1、把文件先存储到磁盘的某个目录中！
		//2、把文件的有关信息（名称，类型，上传时间）包装成Attachment[]类型
		//3、把包装好的Attachment[]类型，放到allParams中

		try {
			//首先，判断是否multipart编码类型
			boolean isMultipart = ServletFileUpload.isMultipartContent(request);
			if(!isMultipart){
				allParams = request.getParameterMap();
			}else{
				allParams = new HashMap();
				ServletFileUpload upload = new ServletFileUpload();
				FileItemIterator iter = upload.getItemIterator(request);
				while(iter.hasNext()){
					FileItemStream item = iter.next();
					//得到表单域的名称
				    String name = item.getFieldName();
				    //得到表单域的值（这是一个输入流）
				    InputStream stream = item.openStream();
				    
				    //如果是普通表单域
				    if(item.isFormField()){
				    	String value = Streams.asString(stream,request.getCharacterEncoding());
				    	addFieldsAndValuesToMap(name, value);
				    }else{ //如果是文件
				    	if(stream.available() != 0){//如果文件域没有选择文件，则忽略处理
					    	String filename = item.getName(); //得到上传的文件名称
					    	if(filename != null){
					    		//因为在IE下面，上传的文件还包含有此文件在客户端机器的路径
					    		//所以，要把这个路径去掉，只取文件名
					    		filename = FilenameUtils.getName(filename);
					    	}
					    	//将上传文件的输入流输出到磁盘的文件上
					    	Streams.copy(stream, new FileOutputStream(Attachment.ATTACHMENT_DIR+filename), true);
					    	
					    	Attachment attachment = new Attachment();
					    	attachment.setContentType(item.getContentType());
					    	attachment.setName(filename);
					    	attachment.setUploadTime(new Date());
					    	addFieldsAndValuesToMap(name, attachment);
				    	}
				    }
				}
			}
		} catch (Exception e) {
			e.printStackTrace();
		}		
	}
	
	private void addFieldsAndValuesToMap(String name,String value){
		String[] fieldValues = (String[])allParams.get(name);
		if(fieldValues == null){
			allParams.put(name, new String[]{value});
		}else{
			//比如原来数组：["1","2"]
			//扩充之后：["1","2",null]
			fieldValues = Arrays.copyOf(fieldValues, fieldValues.length+1);
			fieldValues[fieldValues.length - 1] = value;
			allParams.put(name, fieldValues);
		}
	}
	
	private void addFieldsAndValuesToMap(String name,Attachment value){
		Attachment[] fieldValues = (Attachment[])allParams.get(name);
		if(fieldValues == null){
			allParams.put(name, new Attachment[]{value});
		}else{
			//比如原来数组：["1","2"]
			//扩充之后：["1","2",null]
			fieldValues = Arrays.copyOf(fieldValues, fieldValues.length+1);
			fieldValues[fieldValues.length - 1] = value;
			allParams.put(name, fieldValues);
		}
	}	

	@Override
	public String getParameter(String name) {
		String[] values = (String[])allParams.get(name);
		if(values != null){
			return values[0];
		}
		return null;
	}

	@Override
	public Map getParameterMap() {
		return allParams;
	}
}