Socket+JDBC+IO实现java文件上传下载器（上）-原创手记-慕课网

该demo实现的功能有：

用户注册：
注册时输入两次密码，若两次输入不一致，则注册失败，需要重新输入。若用户名被注册过，则提示用户重新输入用户名；
用户登录：
需要验证数据库中是否有对应的用户名和密码，若密码输错三次，则终止用户的登录操作；
文件上传：
从本地上传文件到文件数据库中
文件下载：
从数据库中下载文件到本地
文件更新：
根据id可更新数据库中的文件名
文件删除：
根据id删除数据库中某一个文件
看数据库所有文件;
查看文件（根据用户名）;
查看文件（根据文件id）;

代码分为如下四个部分：Entity,Service,Socket,Util
实体包Entity中主要存放用户实体和文件实体
User类：


`package Entity;

import java.io.Serializable;
/**
 * 用户类
 * @author Administrator
 *
 */
public class User implements Serializable{
  //属性
    private int id;
    private String username;
    private String password;
    //方法
    //构造方法
    public User(){
        super();
    }
    public User(String username, String password) {
        super();
        this.username = username;
        this.password = password;
    }
    //Getter,Setter方法
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }

}

文件类：


`package Entity;

import java.io.Serializable;
import java.util.Arrays;
/**
 * 文件实体类
 * @author Administrator
 *
 */
public class FileEntity implements Serializable {
    //属性
    private int fid;
    private String username;// 用户名，方便查看某个用户上传的文件
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    private String fname;
    private byte[] fcontent;
    //方法
   //构造方法
    public FileEntity(){
        super();
    }
    public FileEntity(String username,String fname, byte[] fcontent) {
        super();
        this.username=username;
        this.fname = fname;
        this.fcontent = fcontent;
    }
    //Getter,Setter方法
    public int getFid() {
        return fid;
    }
    public void setFid(int fid) {
        this.fid = fid;
    }
    public String getFname() {
        return fname;
    }
    public void setFname(String fname) {
        this.fname = fname;
    }
    public byte[] getFcontent() {
        return fcontent;
    }
    public void setFcontent(byte[] fcontent) {
        this.fcontent = fcontent;
    }
    @Override
    public String toString() {
        return "FileEntity [fid=" + fid + ", username=" + username + ", fname="
                + fname + "]";
    }

}

Service包:包括用户服务类和文件服务类
UserSevice类包括了与用户相关的注册和登录功能相关的方法

package Service;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import Util.DBUtil;

import Entity.User;

public class UserService {

    private Connection conn=null;
    private PreparedStatement pstmt=null;
    private ResultSet rs=null;
    /**
     * 登陆
     */
    public boolean login(User user){
        String sql="select * from tb_user where username=? and password=?";
        try{
            conn=DBUtil.getConnection();
        pstmt=conn.prepareStatement(sql);
        pstmt.setString(1, user.getUsername());
        pstmt.setString(2, user.getPassword());
        rs=pstmt.executeQuery();
        if(rs.next()){
            return true;
        }
        }catch(SQLException e){
            e.printStackTrace();
        }finally{
            DBUtil.CloseAll(rs, pstmt, conn);
        }
        return false;

    }

    /**
     * 注册
     */
    public void register(User user){
        String sql="insert into tb_user(username,password)value(?,?)";
         try {
                 conn=DBUtil.getConnection();
                pstmt=conn.prepareStatement(sql);
                pstmt.setString(1, user.getUsername());
                pstmt.setString(2, user.getPassword());
                pstmt.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }finally{
            DBUtil.CloseAll(rs, pstmt, conn);
        }
    }
    /**
     * 查找tb_user,查看用户是否已经注册过
     */
    public boolean queryByUsername(String username){
        conn=DBUtil.getConnection();
        String sql="select * from tb_user where username=?";
        try {
            pstmt=conn.prepareStatement(sql);
            pstmt.setString(1, username);
            rs=pstmt.executeQuery();
            if(rs.next()){
                //说明已经被注册过,要求重新填写用户名
                return true;
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return false;
    }
}

文件服务类：

 package Service;

import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

import Entity.FileEntity;
import Util.DBUtil;

public class FileService {
    private Connection conn=null;
    private PreparedStatement pstmt=null;
    private ResultSet rs=null;

    /**
     * 保存文件到数据库，类似用户的注册功能
     * @param fileEntity
     */
    public void saveFile(FileEntity fileEntity){
        String sql="insert into tb_file(username,fname,fcontent)value(?,?,?)";
         try {
                 conn=DBUtil.getConnection();
                pstmt=conn.prepareStatement(sql);
                pstmt.setString(1,fileEntity.getUsername());
                pstmt.setString(2, fileEntity.getFname());
                pstmt.setBytes(3, fileEntity.getFcontent());
                pstmt.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }finally{
            DBUtil.CloseAll(rs, pstmt, conn);
        }

    }
    //查看数据库中的所有文件信息
    public List<FileEntity> queryAll() throws SQLException{
        Connection conn=DBUtil.getConnection();
        StringBuilder sb=new StringBuilder(" select * from tb_file");
         pstmt=conn.prepareStatement(sb.toString());
         rs=pstmt.executeQuery();
         List<FileEntity> fety=new ArrayList<FileEntity>();
         while(rs.next()){
             FileEntity file=new FileEntity();
             file.setFid(rs.getInt("fid"));
             file.setUsername(rs.getString("username"));
             file.setFname(rs.getString("fname"));
             file.setFcontent(rs.getBytes("fcontent"));
             fety.add(file);
         }
         return fety;
    }
    //根据用户名查看用户上传的文件
    public List<FileEntity> queryFile(String user_name) throws SQLException{
    Connection conn = DBUtil.getConnection();
    StringBuilder sb=new StringBuilder(" select * from tb_file");
    sb.append(" where username = ? ");
    pstmt=conn.prepareStatement(sb.toString());
        pstmt.setString(1, user_name);
//      System.out.println(sb.toString());
          rs = pstmt.executeQuery();
        List<FileEntity> fety =new ArrayList<FileEntity>();
        while (rs.next()) {
            FileEntity file=new FileEntity();
            file.setFid(rs.getInt("fid"));
            file.setUsername(rs.getString("username"));
            file.setFname(rs.getString("fname"));
            file.setFcontent(rs.getBytes("fcontent"));
            fety.add(file);
        }
        return fety;
    }
    //根据id查找文件
    public FileEntity queryFileByFid(int fid) throws SQLException {
         conn=DBUtil.getConnection();
         StringBuilder sb=new StringBuilder("");
         sb.append(" select * from tb_file where fid=? ");
         pstmt=conn.prepareStatement(sb.toString());
         pstmt.setInt(1, fid);
//           System.out.println(sb.toString());
         rs=pstmt.executeQuery();
         FileEntity file=null;
         while(rs.next()){
              file=new FileEntity();
             file.setFid(rs.getInt("fid"));
             file.setUsername(rs.getString("username"));
             file.setFname(rs.getString("fname"));
             file.setFcontent(rs.getBytes("fcontent"));
         }
         return file;
    }
    //删除文件
    public void deleteFile(int fid) throws SQLException {
         conn=DBUtil.getConnection();
         StringBuilder sb=new StringBuilder("");
         sb.append(" delete from tb_file where fid=? ");
            pstmt=conn.prepareStatement(sb.toString());
            pstmt.setInt(1,fid);
            pstmt.execute();
    }
    //更新文件
    public void updateFile(FileEntity file) throws SQLException{
         conn=DBUtil.getConnection();
         StringBuilder sb=new StringBuilder("");
         sb.append(" update tb_file set fname=? where fid=? ");
            pstmt=conn.prepareStatement(sb.toString());
            pstmt.setString(1,file.getFname());
            pstmt.setInt(2,file.getFid());
            pstmt.execute();
    }

}

Socket+JDBC+IO实现java文件上传下载器（上）原创