深入分析Java中webwork的文件上传机制

public void service(HttpServletRequest request, HttpServletResponse response) 
throws ServletException {
........

request = wrapRequest(request);
......... 
}

protected HttpServletRequest wrapRequest(HttpServletRequest request) 
throws IOException {
........................

if (MultiPartRequest.isMultiPart(request)) {
request = new MultiPartRequestWrapper(request, getSaveDir(), getMaxSize());
}

return request;
}

public MultiPartRequestWrapper(HttpServletRequest request, String saveDir, int maxSize) 
throws IOException {
.....................

//step3.1)获取webwork.preperties配置的parser
String parser = "";

parser = Configuration.getString("webwork.multipart.parser");

// If it's not set, use Pell
if (parser.equals("")) {
log.warn("Property webwork.multipart.parser not set." +
" Using com.opensymphony.webwork.dispatcher.multipart.PellMultiPartRequest");
parser = "com.opensymphony.webwork.dispatcher.multipart.PellMultiPartRequest";
}
// legacy support for old style property values
else if (parser.equals("pell")) {
parser = "com.opensymphony.webwork.dispatcher.multipart.PellMultiPartRequest";
} else if (parser.equals("cos")) {
parser = "com.opensymphony.webwork.dispatcher.multipart.CosMultiPartRequest";
} else if (parser.equals("jakarta")) {
parser = "com.opensymphony.webwork.dispatcher.multipart.JakartaMultiPartRequest";
}

//step3.2)获取后通过反射实例化parser
try {
Class baseClazz = 
com.opensymphony.webwork.dispatcher.multipart.MultiPartRequest.class;

Class clazz = Class.forName(parser);

// make sure it extends MultiPartRequest
if (!baseClazz.isAssignableFrom(clazz)) {
addError("Class '" + parser + "' does not extend MultiPartRequest");

return;
}

// get the constructor
Constructor ctor = clazz.getDeclaredConstructor(new Class[]{
Class.forName("javax.servlet.http.HttpServletRequest"),
java.lang.String.class, int.class
});

// build the parameter list
Object[] parms = new Object[]{
request, saveDir, new Integer(maxSize)
};

// instantiate it
multi = (MultiPartRequest) ctor.newInstance(parms);
.................................................
}

public JakartaMultiPartRequest(HttpServletRequest servletRequest, String saveDir, int maxSize)
throws IOException {

//设置保存参数
DiskFileUpload upload = new DiskFileUpload();
// we must store all uploads on disk because the ww multipart API is missing streaming
// capabilities
upload.setSizeThreshold(0);
upload.setSizeMax(maxSize);
if (saveDir != null) {
upload.setRepositoryPath(saveDir);
}

// Parse the request
try {

/**此方法生成文件，将请求中的每个参数都生成一个
*临时文件比如upload_00000017.tmp， upload_00000018.tmp等，
*就算是form提交的参数也如此
*/
List items = upload.parseRequest(servletRequest);

......................
}