jdbc 连接mysql的问题

Question

//表已经建好了。
//conn = DriverManager.getConnection(url,user,passwordofDB); 这句总是出现Connection不能转换为Connection。
//望高手指点，谢谢！
import java.sql.*;import com.mysql.jdbc.Connection;
import com.mysql.jdbc.ResultSet;
import com.mysql.jdbc.*;
import com.mysql.jdbc.Statement;
import com.mysql.jdbc.jdbc2.optional.MysqlXid;
public class JdbcDome {
public static void main(String[] args) {
try{
// Class.forName("org.git.mm.mysql.Driver");
// java.sql.DriverManager.registerDriver(new org.git.mm.mysql.Driver());
 Class.forName("com.mysql.jdbc.Driver");
}
catch(java.lang.ClassNotFoundException e)
{
System.out.println("Class Not Found Exception occur.Message is:");
System.out.println(e.getMessage());
}
    try{
Statement stmt;
ResultSet rs;
String url="jdbc:mysql://localhost;8080/test";
String user= "root";
String passwordofDB= "kaka19860205";
Connection conn=null;

     try{
     
     conn = DriverManager.getConnection(url,user,passwordofDB);        
                    
}
catch(Exception e)
{
e.printStackTrace();
}
 stmt=(Statement) conn.createStatement();
 rs=(ResultSet) stmt.executeQuery("select *from userinfo");
 while(rs.next())
 {
 int id=rs.getInt(1);
 String name=rs.getString(2);
 String password=rs.getString(3);
 int age=rs.getInt(4);
 String gender=rs.getString(5);
 String email=rs.getString(6);
 System.out.println("id"+id);
 System.out.println("name"+name);
 System.out.println("password"+password);
 System.out.println("age"+age);
 System.out.println("gender"+gender);
 System.out.println("email"+email);

 }
 rs.close();
 stmt.close();
 conn.close();
 catch(SQLException e)
 {
 System.out.println("Class Not Found Exception occur.Message is:");
System.out.println(e.getMessage());
 }

    
}

Answer 1

import com.mysql.jdbc.Connection;
import com.mysql.jdbc.ResultSet;
import com.mysql.jdbc.*;
import com.mysql.jdbc.Statement; 全部改成java.sql.* 就行了

Answer 2

com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception: ** BEGIN NESTED EXCEPTION ** java.net.UnknownHostException
MESSAGE: localhost;8080STACKTRACE:java.net.UnknownHostException: localhost;8080
at java.net.Inet4AddressImpl.lookupAllHostAddr(Native Method)
at java.net.InetAddress$1.lookupAllHostAddr(InetAddress.java:849)
at java.net.InetAddress.getAddressFromNameService(InetAddress.java:1200)
at java.net.InetAddress.getAllByName0(InetAddress.java:1153)
at java.net.InetAddress.getAllByName(InetAddress.java:1083)
at java.net.InetAddress.getAllByName(InetAddress.java:1019)
at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:246)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:271)
at com.mysql.jdbc.Connection.createNewIO(Connection.java:2744)
at com.mysql.jdbc.Connection.<init>(Connection.java:1553)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285)
at java.sql.DriverManager.getConnection(DriverManager.java:582)
at java.sql.DriverManager.getConnection(DriverManager.java:185)
at JdbcDome.main(JdbcDome.java:30)
** END NESTED EXCEPTION **Last packet sent to the server was 0 ms ago.
at com.mysql.jdbc.Connection.createNewIO(Connection.java:2820)
at com.mysql.jdbc.Connection.<init>(Connection.java:1553)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285)
at java.sql.DriverManager.getConnection(DriverManager.java:582)
at java.sql.DriverManager.getConnection(DriverManager.java:185)
at JdbcDome.main(JdbcDome.java:30)
Exception in thread "main" java.lang.NullPointerException
at JdbcDome.main(JdbcDome.java:39)

Answer 3

com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception: ** BEGIN NESTED EXCEPTION ** java.net.UnknownHostException
MESSAGE: localhost;8080STACKTRACE:java.net.UnknownHostException: localhost;8080
at java.net.Inet4AddressImpl.lookupAllHostAddr(Native Method)
at java.net.InetAddress$1.lookupAllHostAddr(InetAddress.java:849)
at java.net.InetAddress.getAddressFromNameService(InetAddress.java:1200)
at java.net.InetAddress.getAllByName0(InetAddress.java:1153)
at java.net.InetAddress.getAllByName(InetAddress.java:1083)
at java.net.InetAddress.getAllByName(InetAddress.java:1019)
at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:246)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:271)
at com.mysql.jdbc.Connection.createNewIO(Connection.java:2744)
at com.mysql.jdbc.Connection.<init>(Connection.java:1553)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285)
at java.sql.DriverManager.getConnection(DriverManager.java:582)
at java.sql.DriverManager.getConnection(DriverManager.java:185)
at JdbcDome.main(JdbcDome.java:30)
** END NESTED EXCEPTION **Last packet sent to the server was 0 ms ago.
at com.mysql.jdbc.Connection.createNewIO(Connection.java:2820)
at com.mysql.jdbc.Connection.<init>(Connection.java:1553)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285)
at java.sql.DriverManager.getConnection(DriverManager.java:582)
at java.sql.DriverManager.getConnection(DriverManager.java:185)
at JdbcDome.main(JdbcDome.java:30)
Exception in thread "main" java.lang.NullPointerException
at JdbcDome.main(JdbcDome.java:39)

Answer 4

localhost;8080 当中应该是冒号，而不是分号

Answer 5

你的 mysql 怎么会使用 8080 端口啊？奇怪~~~

Answer 6

localhost;8080 当中应该是冒号，而不是分号

Answer 7

/*
该了，还是不行哦。
不知道怎么回事？
没有错误，但运行不起啊、错误代码：：：：com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception: ** BEGIN NESTED EXCEPTION ** com.mysql.jdbc.CommunicationsException
MESSAGE: Communications link failure due to underlying exception: ** BEGIN NESTED EXCEPTION ** java.io.EOFException
MESSAGE: Can not read response from server. Expected to read 4 bytes, read 0 bytes before connection was unexpectedly lost.STACKTRACE:java.io.EOFException: Can not read response from server. Expected to read 4 bytes, read 0 bytes before connection was unexpectedly lost.
at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:1997)
at com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:573)
at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1044)
at com.mysql.jdbc.Connection.createNewIO(Connection.java:2748)
at com.mysql.jdbc.Connection.<init>(Connection.java:1553)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285)
at java.sql.DriverManager.getConnection(DriverManager.java:582)
at java.sql.DriverManager.getConnection(DriverManager.java:185)
at JdbcDome.main(JdbcDome.java:30)
** END NESTED EXCEPTION **Last packet sent to the server was 0 ms ago.STACKTRACE:com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception: ** BEGIN NESTED EXCEPTION ** java.io.EOFException
MESSAGE: Can not read response from server. Expected to read 4 bytes, read 0 bytes before connection was unexpectedly lost.STACKTRACE:java.io.EOFException: Can not read response from server. Expected to read 4 bytes, read 0 bytes before connection was unexpectedly lost.
at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:1997)
at com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:573)
at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1044)
at com.mysql.jdbc.Connection.createNewIO(Connection.java:2748)
at com.mysql.jdbc.Connection.<init>(Connection.java:1553)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285)
at java.sql.DriverManager.getConnection(DriverManager.java:582)
at java.sql.DriverManager.getConnection(DriverManager.java:185)
at JdbcDome.main(JdbcDome.java:30)
** END NESTED EXCEPTION **Last packet sent to the server was 0 ms ago.
at com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:641)
at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1044)
at com.mysql.jdbc.Connection.createNewIO(Connection.java:2748)
at com.mysql.jdbc.Connection.<init>(Connection.java:1553)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285)
at java.sql.DriverManager.getConnection(DriverManager.java:582)
at java.sql.DriverManager.getConnection(DriverManager.java:185)
at JdbcDome.main(JdbcDome.java:30)
** END NESTED EXCEPTION **Last packet sent to the server was 0 ms ago.
at com.mysql.jdbc.Connection.createNewIO(Connection.java:2820)
at com.mysql.jdbc.Connection.<init>(Connection.java:1553)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285)
at java.sql.DriverManager.getConnection(DriverManager.java:582)
at java.sql.DriverManager.getConnection(DriverManager.java:185)
at JdbcDome.main(JdbcDome.java:30)
Exception in thread "main" java.lang.NullPointerException
at JdbcDome.main(JdbcDome.java:39)*/import java.sql.*;
public class JdbcDome {
public static void main(String[] args) {
try{
// Class.forName("org.git.mm.mysql.Driver");
// java.sql.DriverManager.registerDriver(new org.git.mm.mysql.Driver());
 Class.forName("com.mysql.jdbc.Driver");
}
catch(java.lang.ClassNotFoundException e)
{
System.out.println("Class Not Found Exception occur.Message is:");
System.out.println(e.getMessage());
}
    try{
Statement stmt;
ResultSet rs;
String url="jdbc:mysql://localhost:8080/test";
String user= "root";
String passwordofDB= "kaka19860205";
Connection conn=null;

     try{
     
     conn = DriverManager.getConnection(url,user,passwordofDB);        
                    
}
catch(Exception e)
{
e.printStackTrace();
}
 stmt=(Statement) conn.createStatement();
 rs=(ResultSet) stmt.executeQuery("select *from userinfo");
 while(rs.next())
 {
 int id=rs.getInt(1);
 String name=rs.getString(2);
 String password=rs.getString(3);
 int age=rs.getInt(4);
 String gender=rs.getString(5);
 String email=rs.getString(6);
 System.out.println("id"+id);
 System.out.println("name"+name);
 System.out.println("password"+password);
 System.out.println("age"+age);
 System.out.println("gender"+gender);
 System.out.println("email"+email);

 }
 rs.close();
 stmt.close();
 conn.close();
 }
 catch(SQLException e)
 {
 System.out.println("Class Not Found Exception occur.Message is:");
System.out.println(e.getMessage());
 }
}
    
}

Answer 8

你的代码好乱，问题很多，仿照你的重新写了一下。import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;public class Test {
    
    public static void main(String[] args) {
        Connection con = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        try {
            con = ConnectionFactory.getConnection();
            String sql = "SELECT id, name, password, age, gender, email " +
             "FROM userinfo";
            ps = con.prepareStatement(sql);
            rs = ps.executeQuery();
            while(rs.next()) {
                System.out.println("      id = " + rs.getInt("id"));
                System.out.println("    name = " + rs.getString("name"));
                System.out.println("password = " + rs.getString("password"));
                System.out.println("     age = " + rs.getInt("age"));
                System.out.println("  gender = " + rs.getString("gender"));
                System.out.println("   email = " + rs.getString("email"));
                System.out.println();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            if(rs != null) {
                try {
                    rs.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if(ps != null) {
                try {
                    ps.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if(con != null) {
                try {
                    con.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }        
    }
}import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;public class ConnectionFactory {
    
    private final static String JDBC_DRIVER_CLASS = "com.mysql.jdbc.Driver";
    private final static String JDBC_URL          = "jdbc:mysql://localhost:3306/test";
    private final static String DATABASE_USERNAME = "root";
    private final static String DATABASE_PASSWORD = "root";
    
    private ConnectionFactory() {        
    }
    
    public static Connection getConnection() throws SQLException {
        Connection con = null;
        try {
            Class.forName(JDBC_DRIVER_CLASS);
            con = DriverManager.getConnection(
                    JDBC_URL, DATABASE_USERNAME, DATABASE_PASSWORD
                );
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
        return con;
    }
}

Answer 9

你的mysql端口号是3306; 强悍！！！
!

Answer 10

"jdbc:mysql://localhost:3306/test";当前这个test是？？？

Answer 11

3306是默认的端口啊，如果像lz一样用8080的话，那么的tomcat或者jboss就需要换端口了