本文主要是介绍springmvc+ajaxfileupload实现头像上传并预览，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
实现原理：利用ajaxfileupload.js + springmvc进行图片文件的上传，再利用base64编码技术得到图片的编码字符串，并返回到页面进行img预览。还可以吧编码字符串存入数据库，较大文件不建议存入数据库。(需要jquery支持)
js代码：
/*** 图片上传*/
function ajaxFileUpload() {$.ajaxFileUpload({url:'../../../hr/upload.do', //需要链接到服务器地址secureuri:false,fileElementId:'file', //文件选择框的id属性dataType: 'json', //服务器返回的格式类型success: function (data, status) //成功{ var json = eval("("+data+")");//解析返回的jsonvar imageCode = json.imageCode;if(imageCode!='-1'){$("#showImg").attr("src", imageCode); $("#input_photo").val(imageCode);}else{alert("上传失败！只允许上传图片类型(jpg,gif,png)且小于1M的照片");}},error: function (data, status, e) //异常{alert("出错了，请重新上传！");}});
}
java代码：
import java.io.IOException;
import java.io.PrintWriter;
import java.util.HashMap;
import java.util.Map;import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.multipart.commons.CommonsMultipartFile;import com.cpeam.hr.util.ImageUtil;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;/*** 图片上传控制器* @author tanfei* @date 2013-09-23*/
@Controller
@RequestMapping("/hr")
public class ImgUploadAction {@RequestMapping(value="uploadImg")public void uploadImg() {}/*** 上传* @param file* @param request* @param model* @return*/@RequestMapping(value="/upload",method=RequestMethod.POST)public void fileUpload(@RequestParam("file")CommonsMultipartFile file,HttpServletRequest request,HttpServletResponse response){ //图片文件上传Map<String, Object> resMap = new HashMap<String, Object>();String imageCode = "-1";//默认上传失败/**判断文件是否为空,空直接返回上传错误**/if(!file.isEmpty()){//获得文件后缀名String suffix = file.getOriginalFilename().substring(file.getOriginalFilename().lastIndexOf("."));if(suffix.equals(".jpg") || suffix.equals(".gif") || suffix.equals(".png")) {//检测图片类型if(file.getSize() > 1000000) {imageCode = "-1";//throw new Exception("上传失败：文件大小不能超过1M");}else {try {//将上传的图片转换成base64编码字符串imageCode = "data:image/gif;base64," + ImageUtil.encodeImageToStr(file.getInputStream());} catch (IOException e) {e.printStackTrace();}}}}else{imageCode = "-1";}resMap.put("imageCode", imageCode);response.setContentType("text/html;charset=UTF-8");//指定响应内容类型，避免<pre...try {PrintWriter out = response.getWriter();Gson gson = new GsonBuilder().create();String gsonStr = gson.toJson(resMap);out.write(gsonStr);out.flush();} catch (IOException e) {e.printStackTrace();}}}
springmvc文件配置：
<!-- 文件上传相关start tanfei 2013-09-20--><!-- SpringMVC上传文件时，需要配置MultipartResolver处理器 --><bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver"> <!-- 指定所上传文件的总大小不能超过200KB。注意maxUploadSize属性的限制不是针对单个文件，而是所有文件的容量之和 --><property name="maxUploadSize" value="200000"/> </bean> <!-- SpringMVC在超出上传文件限制时，会抛出org.springframework.web.multipart.MaxUploadSizeExceededException --> <!-- 该异常是SpringMVC在检查上传的文件信息时抛出来的，而且此时还没有进入到Controller方法中 --><bean id="exceptionResolver" class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver"> <property name="exceptionMappings"> <props> <!-- 遇到MaxUploadSizeExceededException异常时，自动跳转到/WEB-INF/jsp/error_fileupload.jsp页面 --><prop key="org.springframework.web.multipart.MaxUploadSizeExceededException">error_fileupload</prop> <prop key="java.lang.Exception">error_all</prop></props> </property></bean><!-- 文件上传相关end -->jquery插件ajaxfileupload.js:
jQuery.extend({createUploadIframe: function(id, uri){//create framevar frameId = 'jUploadFrame' + id;var iframeHtml = '<iframe id="' + frameId + '" name="' + frameId + '" style="position:absolute; top:-9999px; left:-9999px"';if(window.ActiveXObject){if(typeof uri== 'boolean'){iframeHtml += ' src="' + 'javascript:false' + '"';}else if(typeof uri== 'string'){iframeHtml += ' src="' + uri + '"';} }iframeHtml += ' />';jQuery(iframeHtml).appendTo(document.body);return jQuery('#' + frameId).get(0); },createUploadForm: function(id, fileElementId,data){//create form var formId = 'jUploadForm' + id;var fileId = 'jUploadFile' + id;var form = jQuery('<form action="" method="POST" name="' + formId + '" id="' + formId + '" enctype="multipart/form-data"></form>'); var oldElement = jQuery('#' + fileElementId);var newElement = jQuery(oldElement).clone();jQuery(oldElement).attr('id', fileId);jQuery(oldElement).before(newElement);jQuery(oldElement).appendTo(form);/***** 增加参数的支持 *****/ if (data) { for (var i in data) { $('<input type="hidden" name="' + i + '" value="' + data[i] + '" />').appendTo(form); } }//set attributesjQuery(form).css('position', 'absolute');jQuery(form).css('top', '-1200px');jQuery(form).css('left', '-1200px');jQuery(form).appendTo('body'); return form;},ajaxFileUpload: function(s) {// TODO introduce global settings, allowing the client to modify them for all requests, not only timeout s = jQuery.extend({}, jQuery.ajaxSettings, s);var id = new Date().getTime();// ADD s.datavar form = jQuery.createUploadForm(id, s.fileElementId, s.data);var io = jQuery.createUploadIframe(id, s.secureuri);var frameId = 'jUploadFrame' + id;var formId = 'jUploadForm' + id; // Watch for a new set of requestsif ( s.global && ! jQuery.active++ ){jQuery.event.trigger( "ajaxStart" );} var requestDone = false;// Create the request objectvar xml = {} if ( s.global )jQuery.event.trigger("ajaxSend", [xml, s]);// Wait for a response to come backvar uploadCallback = function(isTimeout){ var io = document.getElementById(frameId);try { if(io.contentWindow){xml.responseText = io.contentWindow.document.body?io.contentWindow.document.body.innerHTML:null;xml.responseXML = io.contentWindow.document.XMLDocument?io.contentWindow.document.XMLDocument:io.contentWindow.document;}else if(io.contentDocument){xml.responseText = io.contentDocument.document.body?io.contentDocument.document.body.innerHTML:null;xml.responseXML = io.contentDocument.document.XMLDocument?io.contentDocument.document.XMLDocument:io.contentDocument.document;} }catch(e){jQuery.handleError(s, xml, null, e);}if ( xml || isTimeout == "timeout") { requestDone = true;var status;try {status = isTimeout != "timeout" ? "success" : "error";// Make sure that the request was successful or notmodifiedif ( status != "error" ){// process the data (runs the xml through httpData regardless of callback)var data = jQuery.uploadHttpData( xml, s.dataType );// If a local callback was specified, fire it and pass it the dataif ( s.success )s.success( data, status );// Fire the global callbackif( s.global )jQuery.event.trigger( "ajaxSuccess", [xml, s] );} elsejQuery.handleError(s, xml, status);} catch(e) {status = "error";jQuery.handleError(s, xml, status, e);}// The request was completedif( s.global )jQuery.event.trigger( "ajaxComplete", [xml, s] );// Handle the global AJAX counterif ( s.global && ! --jQuery.active )jQuery.event.trigger( "ajaxStop" );// Process resultif ( s.complete )s.complete(xml, status);jQuery(io).unbind()setTimeout(function(){ try {jQuery(io).remove();jQuery(form).remove(); } catch(e) {jQuery.handleError(s, xml, null, e);} }, 100)xml = null}}// Timeout checkerif ( s.timeout > 0 ) {setTimeout(function(){// Check to see if the request is still happeningif( !requestDone ) uploadCallback( "timeout" );}, s.timeout);}try {var form = jQuery('#' + formId);jQuery(form).attr('action', s.url);jQuery(form).attr('method', 'POST');jQuery(form).attr('target', frameId);if(form.encoding){jQuery(form).attr('encoding', 'multipart/form-data'); }else{ jQuery(form).attr('enctype', 'multipart/form-data'); } jQuery(form).submit();} catch(e) { jQuery.handleError(s, xml, null, e);}jQuery('#' + frameId).load(uploadCallback );return {abort: function () {}}; },/** handleError 方法在jquery1.4.2之后移除了，此处重写改方法 **/handleError: function( s, xhr, status, e ) {// If a local callback was specified, fire itif ( s.error ) {s.error.call( s.context || s, xhr, status, e );}// Fire the global callbackif ( s.global ) {(s.context ? jQuery(s.context) : jQuery.event).trigger( "ajaxError", [xhr, s, e] );}},uploadHttpData: function( r, type ) {//alert("-->" + r.responseText);try{//debugger;var data = !type;data = type == "xml" || data ? r.responseXML : r.responseText;// If the type is "script", eval it in global contextif ( type == "script" ){jQuery.globalEval( data );}// Get the JavaScript object, if JSON is used.if ( type == "json" ){/*** 如果返回的是字符串(JSON格式字符串)，下面会报错，导致无法走入sucess方法 加上\" ***/// eval( "data = " + data );eval("data = \" "+data+" \" ");}// evaluate scripts within htmlif ( type == "html" ){jQuery("<div>").html(data).evalScripts();}}catch(e) {} return data;}})
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