JAVAWEB之文件的上传下载

Posted 2020-09-24 每天进步一点点，好记性不如烂笔头

文件上传下载

文件上传:

本篇文章使用的文件上传的例子使用的都是原生技术，servelt+jdbc+fileupload插件，这也是笔者的习惯，当接触到某些从未接触过的东西时，总是喜欢用最原始的东西将他们表达出来。下面是具体的步骤，大家可以跟着我一步一步的用apache的fileupload插件来完成文件的上传下载。

1.创建一个web工程，我们这里取名为fileupload

2.导入相关jar包，，数据源使用的是apache-c3p0数据源，以及上传下载插件包，goson库，以及mysql驱动包，大家可以去https://mvnrepository.com/自行下载，系在前请核实jar版本，防止jar冲突。

3.src目录下创建upload.properties文件，用于配置文件上传的限制参数。

 

1 exts=pptx,docx,doc
2 file.max.size=1048576
3 total.file.max.size=5242880

 

4.创建工程包结构， 

5.创建读取upload.properties的监听器类，初始化上传文件的限制参数，具体代码如下:

 1 package com.sunyard.listener;
 2 
 3 import java.io.IOException;
 4 import java.io.InputStream;
 5 import java.util.Map;
 6 import java.util.Properties;
 7 
 8 import javax.servlet.ServletContextEvent;
 9 import javax.servlet.ServletContextListener;
10 
11 import com.sunyard.utils.FileUploadAppProperties;
12 
13 /**
14  * <p>初始化上传文件限制参数的监听器</p>
15  * @author:[e-mail]
16  * @date:2017-6-16
17  */
18 public class FileUploadAppListener implements ServletContextListener{
19 
20     @Override
21     public void contextDestroyed(ServletContextEvent arg0) {
22         
23     }
24 
25     @Override
26     public void contextInitialized(ServletContextEvent arg0) {
27         InputStream in = this.getClass().getClassLoader().getResourceAsStream("/upload.properties");
28         
29         Properties properties = new Properties();
30         
31         try {
32             properties.load(in);
33             
34             for(Map.Entry<Object, Object> prop : properties.entrySet()){
35                 String propertyName = (String) prop.getKey();
36                 String propertyValue = (String) prop.getValue();
37                 
38                 FileUploadAppProperties.getInstance().addProperty(propertyName, propertyValue);
39             }
40             
41         } catch (IOException e) {
42             e.printStackTrace();
43         }
44     }
45 
46 }

 

 

 6.配置web.xml文件

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <web-app version="3.0" 
 3     xmlns="http://java.sun.com/xml/ns/javaee" 
 4     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
 5     xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
 6     http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
 7   <display-name></display-name>    
 8   <welcome-file-list>
 9     <welcome-file>index.jsp</welcome-file>
10   </welcome-file-list>
11   
12   <!-- 初始化监听器 -->
13   <listener>
14       <listener-class>com.sunyard.listener.FileUploadAppListener</listener-class>
15   </listener>
16   
17   <!-- 注册上传servlet -->
18   <servlet>
19       <servlet-name>upload</servlet-name>
20       <servlet-class>com.sunyard.servlet.FileUploadServlet</servlet-class>
21   </servlet>
22   <servlet-mapping>
23       <servlet-name>upload</servlet-name>
24       <url-pattern>/upload</url-pattern>
25   </servlet-mapping>
26   
27   <!-- 注册下载servlet -->
28   <servlet>
29      <servlet-name>download</servlet-name>
30      <servlet-class>com.sunyard.servlet.DownLoadServlet</servlet-class>
31   </servlet>
32   <servlet-mapping>
33       <servlet-name>download</servlet-name>
34       <url-pattern>/download</url-pattern>
35   </servlet-mapping>
36   
37 </web-app>

配置监听器，以及文件上传servlet和文件下载servlet。

6.完善工程所需要的类，

1）创建上传下载实体，FileUploadBean

 1 package com.sunyard.bean;
 2 
 3 /**
 4  * <p>文件上传实体</p>
 5  * @author:[e-mail]
 6  * @date:2017-6-16
 7  */
 8 public class FileUploadBean {
 9     private Integer id;
10     // 文件名
11     private String fileName;
12     // 文件的路径
13     private String filePath;
14     // 文件的描述
15     private String fileDesc;
16     
17     public Integer getId() {
18         return id;
19     }
20 
21     public void setId(Integer id) {
22         this.id = id;
23     }
24 
25     public String getFileName() {
26         return fileName;
27     }
28 
29     public void setFileName(String fileName) {
30         this.fileName = fileName;
31     }
32 
33     public String getFilePath() {
34         return filePath;
35     }
36 
37     public void setFilePath(String filePath) {
38         this.filePath = filePath;
39     }
40 
41     public String getFileDesc() {
42         return fileDesc;
43     }
44 
45     public void setFileDesc(String fileDesc) {
46         this.fileDesc = fileDesc;
47     }
48 
49     public FileUploadBean(String fileName, String filePath, String fileDesc) {
50         super();
51         this.fileName = fileName;
52         this.filePath = filePath;
53         this.fileDesc = fileDesc;
54     }
55     
56     public FileUploadBean(Integer id, String fileName, String filePath,
57             String fileDesc) {
58         this.id = id;
59         this.fileName = fileName;
60         this.filePath = filePath;
61         this.fileDesc = fileDesc;
62     }
63 
64     public FileUploadBean() {
65         
66     }
67 }

2）dao操作自定义异常类

 1 package com.sunyard.db;
 2 
 3 public class DBException extends Exception {
 4 
 5     /**
 6      * 
 7      */
 8     private static final long serialVersionUID = -1547402862446161034L;
 9     
10     public DBException() {
11     }
12     
13     public DBException(String msg) {
14         super(msg);
15     }
16     
17     public DBException(String msg, Exception ex) {
18         super(msg, ex);
19     }
20 }

3）JDBC连接工具类

 1 package com.sunyard.db;
 2 
 3 import java.io.InputStream;
 4 import java.sql.Connection;
 5 import java.sql.DriverManager;
 6 import java.sql.ResultSet;
 7 import java.sql.SQLException;
 8 import java.sql.Statement;
 9 import java.util.Properties;
10 
11 public class JDBCUtils {
12     public static void release(ResultSet rs, 
13             Statement statement, Connection conn) {
14         if(rs != null){
15             try {
16                 rs.close();
17             } catch (SQLException e) {
18                 e.printStackTrace();
19             }
20         }
21         
22         
23         if (statement != null) {
24             try {
25                 statement.close();
26             } catch (Exception e2) {
27                 e2.printStackTrace();
28             }
29         }
30 
31         if (conn != null) {
32             try {
33                 conn.close();
34             } catch (Exception e2) {
35                 e2.printStackTrace();
36             }
37         }
38     }
39     
40     /**
41      * 关闭 Statement 和 Connection
42      * @param statement
43      * @param conn
44      */
45     public static void release(Statement statement, Connection conn) {
46         if (statement != null) {
47             try {
48                 statement.close();
49             } catch (Exception e2) {
50                 e2.printStackTrace();
51             }
52         }
53 
54         if (conn != null) {
55             try {
56                 conn.close();
57             } catch (Exception e2) {
58                 e2.printStackTrace();
59             }
60         }
61     }
62 
63     /**
64      * 1. 获取连接的方法. 通过读取配置文件从数据库服务器获取一个连接.
65      * 
66      * @return
67      * @throws Exception
68      */
69     public static Connection getConnection() throws Exception {
70         // 1. 准备连接数据库的 4 个字符串.
71         // 1). 创建 Properties 对象
72         Properties properties = new Properties();
73 
74         // 2). 获取 jdbc.properties 对应的输入流
75         InputStream in = JDBCUtils.class.getClassLoader().getResourceAsStream(
76                 "jdbc.properties");
77 
78         // 3). 加载 2） 对应的输入流
79         properties.load(in);
80 
81         // 4). 具体决定 user, password 等4 个字符串.
82         String user = properties.getProperty("user");
83         String password = properties.getProperty("password");
84         String jdbcUrl = properties.getProperty("jdbcUrl");
85         String driver = properties.getProperty("driver");
86 
87         // 2. 加载数据库驱动程序(对应的 Driver 实现类中有注册驱动的静态代码块.)
88         Class.forName(driver);
89 
90         // 3. 通过 DriverManager 的 getConnection() 方法获取数据库连接.
91         return DriverManager.getConnection(jdbcUrl, user, password);
92     }
93 }

5）文件上传下载的dao层方法

 1 package com.sunyard.db;
 2 
 3 import java.sql.Connection;
 4 import java.sql.ResultSet;
 5 import java.util.ArrayList;
 6 import java.util.List;
 7 
 8 import com.mysql.jdbc.PreparedStatement;
 9 import com.mysql.jdbc.Statement;
10 import com.sunyard.bean.FileUploadBean;
11 
12 /**
13  * <p>文件上传下载dao</p>
14  * @author:[e-mail]
15  * @date:2017-6-25
16  */
17 public class UploadFileDao {
18     
19     /**
20      * 查询所有文件信息
21      * @return
22      */
23     public List<FileUploadBean> getFiles(){
24         Connection conn = null;
25         Statement statement = null;
26         ResultSet rs = null;
27         
28         List<FileUploadBean> beans = new ArrayList<FileUploadBean>();
29         
30         try {
31             conn = JDBCUtils.getConnection();
32             String sql = "SELECT id, file_name fileName, file_path filePath, " +
33                     "file_desc fileDesc FROM upload_files";
34             statement = (Statement) conn.createStatement();
35             rs = statement.executeQuery(sql);
36             
37             while(rs.next()){
38                 Integer id = rs.getInt("id");
39                 String fileName = rs.getString("file_name");
40                 String filePath = rs.getString("file_path");
41                 String fileDesc = rs.getString("file_desc");
42                 
43                 FileUploadBean bean = new FileUploadBean(id, fileName, filePath, fileDesc);
44                 beans.add(bean);
45             }
46         } catch (Exception e) {
47             e.printStackTrace();
48         } finally{
49             JDBCUtils.release(rs, statement, conn);
50         }
51         
52         return beans;
53     } 
54     
55     /**
56      * 将已经上传的文件存放数据库中
57      * @param uploadFiles
58      */
59     public void save(List<FileUploadBean> uploadFiles){
60         
61         Connection conn = null;
62         PreparedStatement preparedStatement = null;
63         
64         try {
65             conn = JDBCUtils.getConnection();
66             String sql = "INSERT INTO upload_files (file_name, file_path, file_desc) VALUES " +
67                     "(?, ?, ?)";
68             preparedStatement = (PreparedStatement) conn.prepareStatement(sql);
69             
70             for(int i = 0;i < uploadFiles.size();i++){
71                 FileUploadBean fileUploadBean = uploadFiles.get(i);
72                 preparedStatement.setString(1, fileUploadBean.getFileName());
73                 preparedStatement.setString(2, fileUploadBean.getFilePath());
74                 preparedStatement.setString(3, fileUploadBean.getFileDesc());
75                 preparedStatement.executeUpdate();
76             }
77             
78         } catch (Exception e) {
79             e.printStackTrace();
80         } finally{
81             JDBCUtils.release(null, preparedStatement, conn);
82         }
83         
84     }
85 }

6）自定义异常类

 1 package com.sunyard.exception;
 2 
 3 public class InvalidExtNameException extends RuntimeException{
 4 
 5     /**
 6      * 
 7      */
 8     private static final long serialVersionUID = -1478119693559275850L;
 9     
10     public InvalidExtNameException(String msg){
11         super(msg);
12     }
13 }

7）处理文件上传的servlet

  1 package com.sunyard.servlet;
  2 
  3 import java.io.File;
  4 import java.io.FileOutputStream;
  5 import java.io.IOException;
  6 import java.io.InputStream;
  7 import java.io.OutputStream;
  8 import java.io.UnsupportedEncodingException;
  9 import java.util.ArrayList;
 10 import java.util.Arrays;
 11 import java.util.HashMap;
 12 import java.util.List;
 13 import java.util.Map;
 14 import java.util.Random;
 15 
 16 import javax.servlet.ServletException;
 17 import javax.servlet.http.HttpServlet;
 18 import javax.servlet.http.HttpServletRequest;
 19 import javax.servlet.http.HttpServletResponse;
 20 
 21 import org.apache.commons.fileupload.FileItem;
 22 import org.apache.commons.fileupload.disk.DiskFileItemFactory;
 23 import org.apache.commons.fileupload.servlet.ServletFileUpload;
 24 
 25 import com.sunyard.bean.FileUploadBean;
 26 import com.sunyard.db.UploadFileDao;
 27 import com.sunyard.exception.InvalidExtNameException;
 28 import com.sunyard.utils.FileUploadAppProperties;
 29 
 30 public class FileUploadServlet extends HttpServlet{
 31 
 32     private static final long serialVersionUID = 6227133615299280663L;
 33     
 34     private static final String FILE_PATH = "/WEB-INF/files/";//类路径
 35     
 36     private static final String TEMP_DIR = "d:\\\\tempDirectory";//文件临时存储路径
 37     
 38     UploadFileDao uploadFileDao = new UploadFileDao();
 39 
 40     @Override
 41     protected void doPost(HttpServletRequest request, HttpServletResponse response)
 42             throws ServletException, IOException {
 43         request.setCharacterEncoding("UTF-8");
 44         
 45         String path = null;
 46         
 47         //获取 ServletFileUpload 对象. 
 48         ServletFileUpload upload = getServletFileUpload();
 49         
 50         try {
 51             //把需要上传的 FileItem 都放入到该 Map 中
 52             //键: 文件的待存放的路径, 值: 对应的 FileItem 对象
 53             Map<String, FileItem> uploadFiles = new HashMap<String, FileItem>();
 54             
 55             //解析请求, 得到 FileItem 的集合.
 56             List<FileItem> items = upload.parseRequest(request);
 57             
 58             //1. 构建 FileUploadBean 的集合, 同时填充 uploadFiles
 59             List<FileUploadBean> beans = buildFileUploadBeans(items, uploadFiles);
 60             
 61             //2. 校验扩展名:
 62             vaidateExtName(beans);
 63             
 64             //3. 校验文件的大小: 在解析时, 已经校验了, 我们只需要通过异常得到结果. 
 65             
 66             //4. 进行文件的上传操作.
 67             upload(uploadFiles);
 68             
 69             //5. 把上传的信息保存到数据库中
 70             saveBeans(beans);
 71             
 72             path = "/app/success.jsp";
 73         } catch (Exception e) {
 74             e.printStackTrace();
 75         }
 76         
 77         request.getRequestDispatcher(path).forward(request, response);
 78     }
 79     
 80     private void saveBeans(List<FileUploadBean> beans) {
 81         uploadFileDao.save(beans);
 82     }
 83 
 84     /**
 85      * 进行文件上传操作
 86      * @param uploadFiles
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