ext2.0如何做文件上传？

能成功了         但是       后台 经常造成     session丢失

不知道为什么   

我做了一个struts2的
但是有个问题,form.reset()方法对这个 textField无效,不能重设成空

部分核心代码如下

......................
//图片上传
var logoUploadField = new Ext.form.TextField({
	id:'logoUploadField',
	fieldLabel:'游戏LOGO图片',
	name : 'picture',
	anchor : '90%',
	height: 20,
	inputType:'file'
	}
);
...................
var addForm = new Ext.FormPanel({
         id:'addForm',
	labelAlign : 'top',
	frame : true,
	width : 500,
	//labelWidth : 70,
	url : 'test.action',
	fileUpload: true,

	items : [{
		layout : 'column',// 该FormPanel的layout布局模式为列模式(column),包含2列
		items : [{// 第一列
			columnWidth : 0.5,
			layout : 'form',
			items : [
							gamenameField,developerField,playtypeField
						]

					}, {	// 第二列
						columnWidth : 0.5,
						layout : 'form',
						items : [
							serialField,priceField,typeIdField

						]
					}]
				},logoUploadField,introductionField],

				buttons : [{
					text : '保存',
					disabled : false,
					handler : function() {
						if (addForm.form.isValid()) {
							addForm.form.submit({
								//url : 'AddLevel.action',
								success : function(form, action) {
									form.reset();
									//introductionField.setValue("");
									//logoUploadField.setValue("");
									Ext.MessageBox.alert('保存成功', '222222添加游戏成功！');

								},
								failure : function(form, action) {
									//introductionField.setValue("");
									//logoUploadField.setValue("");
									Ext.MessageBox.alert('保存失败', '添加游戏失败！');
								},
								waitMsg : '正在保存数据，稍后...'
							});

							addGameFormWin.hide();
						} else {
							Ext.Msg.alert('信息', '请填写完成再提交!');
						}
					}
				}, {
					text : '取消',
					handler : function() {
						//addForm.getForm().reset();
						addGameFormWin.hide();
					}
				}]
			});

action代码如下:

public class ConsoleGameAction extends ActionSupport {

	private String gamename;
	private String serial;
	private String developer;
	private String price;
	private String typeId;
	private String playtype;
	private String introduction;
	private File picture;
	private String pictureContentType;
	private String pictureFileName;
	private String savePath;

	private String jsonString;

	private GameService gameService;


	public String addGame() throws Exception{
		FileOutputStream fos = new FileOutputStream(getSavePath() + "\\" + getPictureFileName());
		FileInputStream fis = new FileInputStream(getPicture());
		byte[] buffer = new byte[1024];
		int len = 0;
		while((len = fis.read(buffer)) > 0){
			fos.write(buffer, 0, len);
		}
		StringBuilder temp = new StringBuilder("{success:true}");
		this.jsonString = temp.toString();
		return SUCCESS;
	}



	public String getGamename() {
		return gamename;
	}

	public void setGamename(String gamename) {
		this.gamename = gamename;
	}

	public String getSerial() {
		return serial;
	}

	public void setSerial(String serial) {
		this.serial = serial;
	}

	public String getDeveloper() {
		return developer;
	}

	public void setDeveloper(String developer) {
		this.developer = developer;
	}

	public String getPrice() {
		return price;
	}

	public void setPrice(String price) {
		this.price = price;
	}

	public String getTypeId() {
		return typeId;
	}

	public void setTypeId(String typeId) {
		this.typeId = typeId;
	}

	public String getPlaytype() {
		return playtype;
	}

	public void setPlaytype(String playtype) {
		this.playtype = playtype;
	}

	public String getIntroduction() {
		return introduction;
	}

	public void setIntroduction(String introduction) {
		this.introduction = introduction;
	}

	public File getPicture() {
		return picture;
	}

	public void setPicture(File picture) {
		this.picture = picture;
	}



	public String getPictureContentType() {
		return pictureContentType;
	}

	public void setPictureContentType(String pictureContentType) {
		this.pictureContentType = pictureContentType;
	}

	public String getPictureFileName() {
		return pictureFileName;
	}

	public void setPictureFileName(String pictureFileName) {
		this.pictureFileName = pictureFileName;
	}

	@SuppressWarnings("deprecation")
	public String getSavePath() {
		return ServletActionContext.getRequest().getRealPath(savePath);
	}

	public void setSavePath(String savePath) {
		this.savePath = savePath;
	}

	public String getJsonString() {
		return jsonString;
	}


	public void setJsonString(String jsonString) {
		this.jsonString = jsonString;
	}


	public GameService getGameService() {
		return gameService;
	}

	public void setGameService(GameService gameService) {
		this.gameService = gameService;
	}



}

action配置

<action name="addgame" class="consoleGameAction" method="addGame">
			<param name="savePath">/upload</param>
			<result name="success">/WEB-INF/console/json_data.jsp</result>
		</action>

哪位能帮我解决下我的问题?将file的textField设成空?

setValue("")也无效

偶直接用smartupload，在一个总的控制器中判断有文件则保存。
然后提取request参数，并将文件保存前后的名称加到Map中，
传递到后面的business层