Android Studio连接数据库实现增删改查

　　　　

 源代码如下:

DBUtil.java：

package dao;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.sql.PreparedStatement;
public class DBUtil {

    public static String db_url = "jdbc:mysql://localhost:3306/test?useSSL=false&characterEncoding=UTF-8&serverTimezone=GMT";
    public static String db_user = "root";
    public static String db_pass = "root";

    public static Connection getConn () {
        Connection conn = null;

        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
            conn = DriverManager.getConnection(db_url, db_user, db_pass);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return conn;
    }

    public static void close (Statement state, Connection conn) {
        if (state != null) {
            try {
                state.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

        if (conn != null) {
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

    public static void close (ResultSet rs, Statement state, Connection conn) {
        if (rs != null) {
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

        if (state != null) {
            try {
                state.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

        if (conn != null) {
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
    
}

 Add.java：

package add;


import java.sql.Connection;
import java.sql.Statement;

import dao.DBUtil;

public class Add {
    public static boolean add(String table, AddService user ) {
        String sql = "insert into "+table+"(username,password)values('" + user.getUsername() + "','" + user.getPassword() + "')";
        Connection conn = DBUtil.getConn();
        Statement state = null;
        boolean f = false;
        int a = 0;
        try {
            state = conn.createStatement();
            a = state.executeUpdate(sql);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(state, conn);
        }
        if (a > 0) {
            f = true;
        }
        return f;
    }
}

AddService.java：

package add;

public class AddService {
    String username;
    String password;

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }
    public static void main(String args[]){
        AddService user=new AddService();
        user.setUsername("123");
        user.setPassword("456");
        Add test=new Add();
        test.add("user1",user);
    }
}

Delete.java：

package delete;

import java.sql.Connection;
import java.sql.Statement;
import java.sql.SQLException;

import dao.DBUtil;

public class Delete {
    public boolean delete(String table,String username)
    {
        boolean c=false;
        Connection conn= DBUtil.getConn();
        Statement state=null;
        String sql="delete from "+table+" where username="+username;
        try {
            state=conn.createStatement();
            int num = state.executeUpdate(sql);
            if(num!=0)
            {
                c= true;
            }
            state.close();
            conn.close();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return c;
    }

}

DeleteService.java：

package delete;

public class DeleteService {
    String username;

    public void setUsername(String username) {
        this.username = username;
    }

    public String getUsername() {
        return username;
    }
    public static void main(String args[]){
        DeleteService user=new DeleteService();
        user.setUsername("123");
        String username="'"+user.getUsername()+"'";
        Delete test=new Delete();
        test.delete("user1",username);
    }
}

Change.java：

package change;

import java.sql.Connection;
import java.sql.SQLException;
import java.sql.Statement;
import dao.DBUtil;
public class Change {
    public boolean change(String table,String lie,String lie0,String gai,String biao)
    {
        Connection conn=DBUtil.getConn();
        Statement state=null;
        try {
            state=conn.createStatement();
            String sql="update "+table+" set "+lie+"='"+gai+"' where "+lie0+"='"+biao+"'";
            System.out.println(sql);
            state.executeUpdate(sql);
            state.close();
            conn.close();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }


        return true;
    }
}

ChangeService.java：

package change;

public class ChangeService {
    String lie;
    String lie0;
    String gai;
    String biao;

    public String getBiao() {
        return biao;
    }
    public String getGai() {
        return gai;
    }

    public String getLie() {
        return lie;
    }

    public String getLie0() {
        return lie0;
    }

    public void setBiao(String biao) {
        this.biao = biao;
    }

    public void setGai(String gai) {
        this.gai = gai;
    }

    public void setLie(String lie) {
        this.lie = lie;
    }

    public void setLie0(String lie0) {
        this.lie0 = lie0;
    }

    public static void main(String args[]){
        ChangeService user=new ChangeService();
        user.setBiao("2");
        user.setGai("xhj");
        user.setLie0("username");
        user.setLie("password");
        Change test=new Change();
        test.change("user1",user.getLie(),user.getLie0(),user.getGai(),user.getBiao());
    }
}

Select.java：

package select;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import dao.DBUtil;
public class Select {
    public boolean  select(String table)
    {
        boolean c;
        Connection conn=DBUtil.getConn();
        Statement state=null;
        try
        {
            state=conn.createStatement();
            String sql="select * from "+table;
            ResultSet rs=state.executeQuery(sql);
            while(rs.next())
            {
                System.out.println(rs.getString(1)+" "+rs.getString(2));
            }
            rs.close();
            state.close();
            conn.close();

        }
        catch(Exception e)
        {

        }
        return true;
    }
}

SelectService.java：

package select;

public class SelectService {
    String table;

    public String getTable() {
        return table;
    }

    public void setTable(String table) {
        this.table = table;
    }
    public static void main(String[] args) {
        SelectService user=new SelectService();
        user.setTable("user1");
        Select test=new Select();
        test.select(user.getTable());
    }
}

数据库表名：user1