Java连接数据库

需要加入JDBC的jar包
如有多个数据库可在IP后加"/数据库名"

package pltools.util;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;

public class MysqlUtil {

    String url;
    String driver;
    String userName;
    String password;
    Connection connection;

    public MysqlUtil() {
        super();
        String[] dbInfo = null;
        try {
            dbInfo = FileUtil.read("db.txt").split("
");
        } catch (Exception e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }
        if (dbInfo.length > 0) {
            driver = dbInfo[0].split("=")[1];
            url = dbInfo[1].split("=")[1];
            userName = dbInfo[2].split("=")[1];
            password = dbInfo[3].split("=")[1];
        } else {
            System.err.println("error : dbInfo is empty");
        }
        String dbString = dbInfo[0] + "
" + dbInfo[1] + "
" + dbInfo[2] + "
" + dbInfo[3] + "
";
        FileUtil.write("sqlLog.txt", "dbInfo:
" + dbString, false);
    }

    public MysqlUtil(String ip) {
        super();
        if (ip.trim().length() > 0) {
            // driver = dbInfo[0].split("=")[1];
            // url = dbInfo[1].split("=")[1];
            // userName = dbInfo[2].split("=")[1];
            // password = dbInfo[3].split("=")[1];
            driver = "com.mysql.jdbc.Driver";
            url = "jdbc:mysql://" + ip + ":3306/ePMS";
            userName = "root";
            password = "Hwroot@com";
        }
        String dbString = driver + "
" + url + "
" + userName + "
" + password + "
";
        FileUtil.write("sqlLog.txt", "dbInfo:
" + dbString, false);
    }

    private Connection getConnection() {
        Connection conn = null;
        try {
            Class.forName(driver);
            conn = DriverManager.getConnection(url, userName, password);
        } catch (Exception e) {
            FileUtil.write("sqlLog.txt", new Date() + "  getConnection Error:
" + e.toString() + "
");
        }
        return conn;
    }

    public String[] getColumn(String sqlString, int columnIndex) throws SQLException {
        String[][] result = executeQuery(sqlString);
        String[] arr = new String[result.length];
        for (int i = 0; i < result.length; i++) {
            arr[i] = result[i][columnIndex];
        }
        return arr;
    }

    public String[][] executeQuery(String sqlString) throws SQLException {
        ResultSet rs = null;
        Connection conn = getConnection();
        List<String[]> list = new ArrayList<String[]>();
        try {
            Statement smt = conn.createStatement();
            if (sqlString.contains("?")) {
                String sql = sqlString.split("\?")[1];
                rs = smt.executeQuery(sql);
            } else {
                rs = smt.executeQuery(sqlString);
            }

            while (rs.next()) {
                ResultSetMetaData rsmd = rs.getMetaData();
                int columnCount = rsmd.getColumnCount();
                String[] strArray = new String[columnCount];
                for (int i = 1; i < columnCount + 1; i++) {
                    strArray[i - 1] = rs.getString(i);
                }
                list.add(strArray);
            }
            conn.close();

        } catch (Exception e) {
            FileUtil.write("sqlLog.txt", new Date() + "  executeQuery  " + sqlString + "  Error:
" + e.toString()
                    + "
");
        }
        String[][] returnArray = new String[list.size()][];
        for (int i = 0; i < returnArray.length; i++) {
            returnArray[i] = (String[]) list.get(i);
        }
        return returnArray;
    }

    public String getSignle(String sqlString) {
        String result = null;
        Connection conn = getConnection();
        List<String> rsList = new ArrayList<String>();

        try {
            Statement smt = conn.createStatement();
            ResultSet rs = null;
            if (sqlString.contains("?")) {
                String sql = sqlString.split("\?")[1];
                rs = smt.executeQuery(sql);
            } else {
                rs = smt.executeQuery(sqlString);
            }
            while (rs.next()) {
                rsList.add(rs.getString(1));
            }
            conn.close();
        } catch (SQLException e) {
            FileUtil.write("sqlLog.txt", new Date() + "  getSignle  " + sqlString + "  Error:
" + e.toString()
                    + "
");
        }
        if (rsList != null && rsList.size() > 0) {
            result = rsList.get(0);
        }
        return result;
    }
}

判断是否连接成功并执行一条查询

package IV;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class DBManager {
    public static void main(String[] args) throws InstantiationException, IllegalAccessException
    {
        String url="jdbc:mysql://10.10.12.24:3306/ePMS";
        String user="system";
        String password="Hwsystem@com";
        String sql;
        String driverclass="com.mysql.jdbc.Driver";//JDBC类名
        try
        {
            //加载JDBC驱动,当这个类被加载时，类加载器会执行该类的静态代码块从而注册驱动程序的一个实例
            Class.forName(driverclass).newInstance();  
            
            //建立数据库的连接
            Connection conn=DriverManager.getConnection(url,user,password);
            if(conn != null){
                System.out.println("连接成功:"+url);
            }
            Statement stmt=conn.createStatement();
            sql="select * from pms_device_t;";
            //stmt.execute("use information_schema;");
            int i=0;
            ResultSet rs1=stmt.executeQuery(sql);
            while (rs1.next())
                i++;
            if(i==0){
                System.out.println("schedule is not excit");
            }else {
                System.out.println("Ok");
                
            }
            ResultSet rs=stmt.executeQuery(sql);
            while (rs.next()){
                System.out.println(rs.getString(1)+"	"+rs.getString(2));
            }
                    
        } catch (Exception e) {
            System.out.println("连接失败:"+url);
        }
        
        
    }
    

}