为什么我要进行上传的图片进行切割呢，我这个项目的图片是部门logo，每个部门都可以选择不同的logo，但是要应对浏览器的兼容以及拉伸，我选择了把一张图片切成左、中、右和剩下的部分，因为左边和中变可能会有图案或者字所以不能拉伸，拉伸的只是右边的部分，剩下的部分自适应就可以了。所以用了javax的ImageReader来操作。最后以blob类型保存数据库中。

首先要在form表单里面写上enctype="multipart/form-data"

<form method="post" id="mainForm" action="${ctx }/admin/department!save.action" enctype="multipart/form-data">

<tr>
				<td style="width: 100px;">
					<strong>上传Logo：</strong>
					<input type="hidden" name="suffix" id="suffix" value=http://www.mamicode.com/"${depart.departmentLogo.suffix }"/>>
图片检查的checkFile()方法用于检查图片是否以规定格式结尾以及是否没有选择
function checkFile(){
		
		var value = http://www.mamicode.com/$("#logoFile").val();>
下面就是进行后台的save操作了。
public String save() throws Exception {
		HttpServletRequest request = ServletActionContext.getRequest() ;
		String departId = request.getParameter("id") ;
		String departName = request.getParameter("name") ;
		String companyId = request.getParameter("companyId") ;
		//图片后缀
		String suffix = request.getParameter("suffix");
		List<Menu> listMenu = new ArrayList<Menu>() ;
		Company company = new Company() ;
		company.setId(Long.valueOf(companyId)) ;
		if(this.logoFile != null && departName != null && companyId != null && suffix != null){
			//获取解析图片的ImageReader
			Iterator<ImageReader> imageReaders = ImageIO.getImageReadersByFormatName(suffix);
			ImageReader imageReader = imageReaders.next();
			//把图片以字节流的形式传入
			InputStream logoStream = new BufferedInputStream(new FileInputStream(this.logoFile));
			//转为图片输入流
			ImageInputStream imageInputStream = ImageIO.createImageInputStream(logoStream);
			imageReader.setInput(imageInputStream, true);
			int imageWidth = imageReader.getWidth(0);
			//固定高度80
			int imageHeight = 80;
			//设置左中右和剩下的宽度
			int leftWidth = imageWidth / 2;
			int middleWidth = (imageWidth - leftWidth) / 3;
			int rightWidth = 5;
			int retainWidth = imageWidth - leftWidth -middleWidth - 5;
			
			ImageReadParam readParam = imageReader.getDefaultReadParam();
			BufferedImage bImage = null;
			//裁剪左半部分
			//根据宽和高获得矩形
			Rectangle leftImageRectangle = new Rectangle(0, 0, leftWidth, imageHeight);
			readParam.setSourceRegion(leftImageRectangle);
			bImage = imageReader.read(0, readParam); 
			//字节数组输出流
			ByteArrayOutputStream leftByteArrayOutputStream = new ByteArrayOutputStream();
			ImageIO.write(bImage, suffix, leftByteArrayOutputStream);
			//获得字节数组
			byte[] leftImageData = http://www.mamicode.com/leftByteArrayOutputStream.toByteArray();>
下面就是显示了，我是用的qui，所以在top.jsp上面的css中进行动态显示
<style type="text/css">
		.welcome-hide{width: 210px;white-space: nowrap;overflow: hidden;text-overflow: ellipsis;}
		#leftLogo{background: url(${ctx }/admin/department-logo!showLogo.action?position=left) no-repeat;width: ${leftWidth}px;height: 80px;}
		#middleLogo{background: url(${ctx }/admin/department-logo!showLogo.action?position=middle) no-repeat;width: ${middleWidth}px;height: 80px;}
		#rightLogo,#topTableStyle{background: url(${ctx }/admin/department-logo!showLogo.action?position=right) repeat-x;height: 80px;}
		#retainLogo{background: url(${ctx }/admin/department-logo!showLogo.action?position=retain) no-repeat;width: ${retainWidth}px;height: 80px;}
	</style>
department-logo!showLogo.action中的showLogo方法就是加载图片的方法
public String showLogo() {
		
		HttpServletRequest request = ServletActionContext.getRequest();
		LoginUser loginUser = (LoginUser)((SecurityContext)request.getSession().
				getAttribute("SPRING_SECURITY_CONTEXT")).getAuthentication().getPrincipal();
		List<DepartmentLogo> logos = this.logoManager.findAll();
		for (DepartmentLogo departmentLogo : logos) {
			if (loginUser.getUser().getDepartment().getId().equals(departmentLogo.getDepartment().getId())) {
				String param = request.getParameter("position");
				Blob blob = null;
				if (param != null) {
					try {
						if (param.equals("left")) {
							blob = departmentLogo.getLeftPartImage();
							imageLogo = blob.getBinaryStream();
							return "showLogo";
						}else if (param.equals("middle")) {
							blob = departmentLogo.getMiddlePartImage();
							imageLogo = blob.getBinaryStream();
							return "showLogo";
						}else if (param.equals("right")) {
							blob = departmentLogo.getRightPartImage();
							imageLogo = blob.getBinaryStream();
							return "showLogo";
						}else if (param.equals("retain")) {
							blob = departmentLogo.getRetainPartImage();
							imageLogo = blob.getBinaryStream();
							return "showLogo";
						}
					} catch (Exception e) {
						e.printStackTrace();
					}
				}
			}
		}
		
		return null;
	}

当然返回的地址应该选择struts2中的type="stream"
@Results({
	@Result(name = "showLogo", type = "stream", params = {"contentType", "image/jpeg,"
			+ "image/bmp,image/png,image/gif,image/jpeg", 
			"inputName", "imageLogo", "bufferSize", "4096"})
})

那么top.jsp中的width是怎么得到的呢？
实在加载菜单的时候得到的，下面是menu中的方法
 HttpServletRequest request = ServletActionContext.getRequest();
			List<DepartmentLogo> logos = this.logoManager.findAll();
			for (DepartmentLogo departmentLogo : logos) {
				if (user.getDepartment().getId().equals(departmentLogo.getDepartment().getId())) {
					request.setAttribute("leftWidth", ImageIO.read(departmentLogo.
							getLeftPartImage().getBinaryStream()).getWidth());
					request.setAttribute("middleWidth", ImageIO.read(departmentLogo.
							getMiddlePartImage().getBinaryStream()).getWidth());
					request.setAttribute("retainWidth", ImageIO.read(departmentLogo.
							getRetainPartImage().getBinaryStream()).getWidth());
					break;
				}
			}

这样就完成了一个上传显示功能。
这个就是我上传的测试图片。

java实现上传图片进行切割