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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

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>

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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();     
     }    

}

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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();
    }    

}

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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;   
             }   
         }
     }

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