java数据库查找代码,JAVA查询数据库

java链接MYSQL数据库并实现查找数据代码如何写？

首先创建一个连接工厂import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.ResultSet;

import java.sql.Statement;public class ConnectionFactory {

private Connection conn=null;

private Statement stmt=null;

private ResultSet rs=null;

public ConnectionFactory() {

super();

// TODO Auto-generated constructor stub

} public void OpenConn() throws Exception{

try{

Class.forName("com.mysql.jdbc.Driver").newInstance();

String url="jdbc:mysql://127.0.0.1:3306/guestbook";

String user="root";

String password="root";

conn=DriverManager.getConnection(url,user,password);

}catch(Exception e){

System.out.println("创建链接抛出异常为："+e.getMessage());

}

} public ResultSet executeQuery(String sql) throws Exception{

try{

stmt=conn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_UPDATABLE);

rs=stmt.executeQuery(sql);

}catch(Exception e){

System.out.println("执行查询抛出的异常为:"+e.getMessage());

}

return rs;

} public void close() throws Exception{

try{

rs.close();

stmt.close();

conn.close();

}catch(Exception e){

System.out.println("关闭对象抛出的异常："+e.getMessage());

}

} }

测试类 import java.sql.ResultSet;public class TestJDBC {

public static void main(String[] args) {

ConnectionFactory c= new ConnectionFactory();

try {

c.OpenConn();

String sql="select * from tb_guestbook";

ResultSet rs=c.executeQuery(sql);

while(rs.next()){

System.out.println(rs.getString(2));

}

c.close();

System.out.println();

} catch (Exception e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

}

相关问答

Q1: JAVA中怎么查询代码？

try{Connection con;

Statement stmt;

ResultSet rs;

int temp;

Class.forName("com.mysql.jdbc.Driver");

con=DriverManager.getConnection("jdbc:mysql://localhost:3306/java","root","");//以上是数据库连接，不同的数据管理器有 //不同的驱动和链接方式，以上是mysql的连接

stmt=con.createStatement();

rs=stmt.executeQuery("select * from student");//执行查询语句，结果赋值给结果集rs

//结果集是结果于字段编号的映射，每一个字

//段都有一个编号，最小为1，也就是第一个字段

while(rs.next()){

String names=rs.getString("name");//查询结果转换成字符串。

System.out.println(names);

}rs.close();

}catch(Exception e){

e.printStackTrace();

}

Q2: 如何用Java实现数据库查询

import java.sql.*;

public class MSSQLText

{

public static void main(String args[])

{

String url="jdbc:microsoft:sqlserver://localhost:1433;DatabaseName=Northwind";

String user="sa";//这里替换成你自已的数据库用户名

String password="sa";//这里替换成你自已的数据库用户密码

String sqlStr="select CustomerID, CompanyName, ContactName from Customers";

try

{ //这里的异常处理语句是必需的.否则不能通过编译!

Class.forName("com.microsoft.jdbc.sqlserver.SQLServerDriver");

System.out.println("类实例化成功!");

Connection con = DriverManager.getConnection(url,user,password);

System.out.println("创建连接对像成功!");

Statement st = con.createStatement();

System.out.println("创建Statement成功!");

ResultSet rs = st.executeQuery(sqlStr);

System.out.println("操作数据表成功!");

System.out.println("----------------!");

while(rs.next())

{

System.out.print(rs.getString("CustomerID") + " ");

System.out.print(rs.getString("CompanyName") + " ");

System.out.println(rs.getString("ContactName"));

}

rs.close();

st.close();

con.close();

}

catch(Exception err){

err.printStackTrace(System.out);

}

}

}

Q3: java连接数据库的代码

package mysql;

import java.sql.*;

/**

* @author xys

*/

public class ConnectMysql {

public static Connection getConnection() throws ClassNotFoundException, SQLException {

String url = "jdbc:mysql://localhost:3306/databaseName";

String user = "mysqluser";

String password = "password";

String driverClass = "com.mysql.cj.jdbc.Driver";

Connection connection = null;

Class.forName(driverClass);

try {

connection = DriverManager.getConnection(url, user, password);

} catch (SQLException e) {

e.printStackTrace();

}

if (connection != null) {

System.out.println("数据库连接成功");

} else {

System.out.println("数据库连接失败");

connection.close();

}

return connection;

}

public void getResult() throws ClassNotFoundException, SQLException {

// 实例化 Statement 对象

Statement statement = getConnection().createStatement();

// 要执行的 Mysql 数据库操作语句（增、删、改、查）

String sql = "";

// 展开结果集数据库

ResultSet resultSet = statement.executeQuery(sql);

while (resultSet.next()) {

// 通过字段检索

int id = resultSet.getInt("id");

String name = resultSet.getString("name");

// 输出数据

System.out.println("ID : " +id);

System.out.println("name :" + name);

}

// 完成后需要依次关闭

resultSet.close();

statement.close();

getConnection().close();

}

}