servlet中获取XMLHttpRequest提交的FormData参数

function SaveProgress(data) {
var fd = new FormData(),
xhr = new XMLHttpRequest();
fd.append('data', data);
xhr.open('post', '/zkvos', true);
xhr.onreadystatechange = function() {
if (xhr.status == 200) {
if (xhr.readyState == 4) {
console.log(xhr.responseText);
}
} else {
console.log('server error');
}
}
xhr.send(fd);
}

package com.study;

import java.io.IOException;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

@WebServlet("/zkvos")
public class StudyOnlineServlet extends HttpServlet {
private static final long serialVersionUID = 1L;

public StudyOnlineServlet() {
super();
}

protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.getWriter().append("parameter error").append(request.getContextPath());
}

protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
Map<String, String> params = this.getParameters(request);
String status = "";
if (this.checkParam(params)) {
String data = params.get("data");//通过参数名拿到参数值
System.out.print(data);
} else {
status = "参数错误";
}
response.getWriter().print(status);
}

/**
* 获取FormData携带参数
*
* @param request
* @return
*/
@SuppressWarnings("unchecked")
private Map<String, String> getParameters(HttpServletRequest request) {
Map<String, String> params = new HashMap<>();
try {
DiskFileItemFactory factory = new DiskFileItemFactory();
ServletFileUpload upload = new ServletFileUpload(factory);
List<FileItem> items;
items = upload.parseRequest(request);
for (FileItem item : items) {
if (item.isFormField()) {
// item.getFieldName();// 参数名
// item.getString();// 参数值
params.put(item.getFieldName(), item.getString());
}
}
} catch (FileUploadException e) {
e.printStackTrace();
}
return params;
}

/**
* 检查参数是否完整
*
* @param params
* @return
*/
@SuppressWarnings("rawtypes")
private Boolean checkParam(Map params) {
String[] paramNames = { "d", "u", "c", "h", "e", "t", "f" };
for (String paramName : paramNames) {
if (params.containsKey(paramName)) {
if (params.get(paramName) == null)
return false;
} else {
return false;
}
}
return true;
}
}