图片上传和文件上传本质上是一样的，图片本身也是文件。文件上传就是将图片上传到服务器，方式虽然有很多，但底层的实现都是文件的读写操作。
注意事项
1.form表单一定要写属性enctype="multipart/form-data"
2.为了能保证文件能上传成功file控件的name属性值要和你提交的控制层变量名一致，
例如空间名是file那么你要在后台这样定义
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private File file; //file控件名
private String fileContentType;//图片类型
private String fileFileName; //文件名
jsp页面
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta http-equiv="pragma" content="no-cache" />
<base target="_self">
<title>文件上传</title>
</head>
<body>
<form method="post" action="" enctype="multipart/form-data">
<input type="file" name="file" value="file">
<input type="submit" value="确定">
</form>
</body>
</html>页面数据需要提交的Controller
package com.cpsec.tang.chemical.action;
import java.io.File;
import java.io.IOException;
import java.util.Random;
import javax.annotation.Resource;
import javax.servlet.http.HttpServletRequest;
import org.apache.commons.io.FileUtils;
import org.apache.struts2.ServletActionContext;
import org.springframework.stereotype.Controller;
import com.cpsec.tang.chemical.biz.LunboBiz;
import com.cpsec.tang.chemical.entity.Image;
import com.opensymphony.xwork2.ActionSupport;
@Controller("lunboAction")
public class LunboAction extends ActionSupport {
/**
*
*/
private static final long serialVersionUID = 1L;
@Resource(name="lunboBiz")
private LunboBiz lunboBiz;
private Image image;
private File file; //file控件名
private String fileContentType;//图片类型
private String fileFileName; //文件名
private Integer number;
public String findImage(){
image=lunboBiz.findImage();
return SUCCESS;
}
public String alterImage(){
image=lunboBiz.findImage();
return SUCCESS;
}
public String alterImage1(){
HttpServletRequest request = ServletActionContext.getRequest();
String root = request.getRealPath("/upload");//图片要上传到的服务器路径
String names[]=fileFileName.split("\.");
String fileName="";
if(names.length>=1){
fileName=getRandomString(20)+"."+names[names.length-1];
}
String picPath="upload/"+fileName;//图片保存到数据库的路径
File file1=new File(root);
try {
FileUtils.copyFile(file, new File(file1,fileName));
}
} catch (IOException e) {
e.printStackTrace();
}
return SUCCESS;
}
/*获取一条随机字符串*/
public String getRandomString(int length) { //length表示生成字符串的长度
String base = "abcdefghijklmnopqrstuvwxyz0123456789";
Random random = new Random();
StringBuffer sb = new StringBuffer();
for (int i = 0; i < length; i++) {
int number = random.nextInt(base.length());
sb.append(base.charAt(number));
}
return sb.toString();
}
}这是通过复制的方式上传文件，还有其他方式
方法二
@Controller("contractAction")
public class ContractAction extends ActionSupport {
private final static String UPLOADDIR = "/files";//文件上传的路径，在webContent下建立
private File file; //input控件名一定为file
//上传文件名集合
private String fileFileName;
//上传文件内容类型集合
private String fileContentType;
private String filename;
public String upload() throws FileNotFoundException, IOException{
String path=uploadFile();//文件保存数据库的路径
return SUCCESS;
}
//执行上传功能
@SuppressWarnings("deprecation")
public String uploadFile() throws FileNotFoundException, IOException {
try {
InputStream in = new FileInputStream(file);
String dir = ServletActionContext.getRequest().getRealPath(UPLOADDIR);
File fileLocation = new File(dir);
//此处也可以在应用根目录手动建立目标上传目录
if(!fileLocation.exists()){
boolean isCreated = fileLocation.mkdir();
if(!isCreated) {
//目标上传目录创建失败,可做其他处理,例如抛出自定义异常等,一般应该不会出现这种情况。
return null;
}
}
// this.setFileFileName(getRandomString(20));
String[] Name=this.getFileFileName().split("\.");
String fileName=getRandomString(20)+"."+Name[Name.length-1];
this.setFileFileName(fileName);
System.out.println(fileName);
File uploadFile = new File(dir, fileName);
OutputStream out = new FileOutputStream(uploadFile);
byte[] buffer = new byte[1024 * 1024];
int length;
while ((length = in.read(buffer)) > 0) {
out.write(buffer, 0, length);
}
in.close();
out.close();
return UPLOADDIR.substring(1)+"\"+fileFileName;
} catch (FileNotFoundException ex) {
return null;
} catch (IOException ex) {
return null;
}
}
public static String getRandomString(int length){
String str="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
Random random=new Random();
StringBuffer sb=new StringBuffer();
for(int i=0;i<length;i++){
int number=random.nextInt(62);
sb.append(str.charAt(number));
}
return sb.toString();
}
}除了单图上传还有多图上传，原理都是一样的
package com.cpsec.tang.chemical.action;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.List;
import javax.servlet.http.HttpServletRequest;
import org.apache.struts2.ServletActionContext;
import com.opensymphony.xwork2.ActionSupport;
/**
* 多文件上传
*/
public class FilesUploadAction extends ActionSupport {
//上传文件存放路径
private final static String UPLOADDIR = "/upload";
//上传文件集合
private List<File> file;
//上传文件名集合
private List<String> fileFileName;
//上传文件内容类型集合
private List<String> fileContentType;
public List<File> getFile() {
return file;
}
public void setFile(List<File> file) {
this.file = file;
}
public List<String> getFileFileName() {
return fileFileName;
}
public void setFileFileName(List<String> fileFileName) {
this.fileFileName = fileFileName;
}
public List<String> getFileContentType() {
return fileContentType;
}
public void setFileContentType(List<String> fileContentType) {
this.fileContentType = fileContentType;
}
public String uploadform() throws Exception {
HttpServletRequest request = ServletActionContext.getRequest();
String webpath=null;//上传路径
for (int i = 0; i < file.size(); i++) {
//循环上传每个文件
uploadFile(i);
webpath="upload/"+this.getFileFileName().get(i);
}
return "SUCCESS";
}
//执行上传功能
private String uploadFile(int i) throws FileNotFoundException, IOException {
try {
InputStream in = new FileInputStream(file.get(i));
String dir = ServletActionContext.getRequest().getRealPath(UPLOADDIR);
File fileLocation = new File(dir);
//此处也可以在应用根目录手动建立目标上传目录
if(!fileLocation.exists()){
boolean isCreated = fileLocation.mkdir();
if(!isCreated) {
//目标上传目录创建失败,可做其他处理,例如抛出自定义异常等,一般应该不会出现这种情况。
return null;
}
}
String fileName=this.getFileFileName().get(i);
File uploadFile = new File(dir, fileName);
OutputStream out = new FileOutputStream(uploadFile);
byte[] buffer = new byte[1024 * 1024];
int length;
while ((length = in.read(buffer)) > 0) {
out.write(buffer, 0, length);
}
in.close();
out.close();
return uploadFile.toString();
} catch (FileNotFoundException ex) {
return null;
} catch (IOException ex) {
return null;
}
}
} 
