Socket+JDBC+IO实现Java文件上传下载器DEMO详解

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;
 }
}

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 + "]";
 }
}

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;
 }
}

 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
 */