SQL数据库连接工具类

package cn.itcast;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ParameterMetaData;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

/**
* 查询结果处理接口
*
* @author 作者：LiuJunGuang
* @version 创建时间：2011-11-10 下午07:26:41
*/
interface ResultSetHander {
Object hander(ResultSet rs);
}

/**
* 类说明：数据库连接和释放
*
* @author 作者: LiuJunGuang
* @version 创建时间：2011-11-6 上午11:49:14
*/
public class JDBCUtils {
private static String driver = "com.mysql.jdbc.Driver";
private static String url = "jdbc:mysql://localhost:3306/chat";
private static String user = "root";
private static String password = "root";
private static Connection con = null;
// 注册驱动
static {
try {
Class.forName(driver);
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}

// 创建连接
public static Connection getConnection() {
if (con == null) {
try {
con = DriverManager.getConnection(url, user, password);
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
return con;
}

// 关闭连接
public static void colse(ResultSet rs, Statement st, Connection con) {
if (rs != null) {
try {
rs.close();
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
if (st != null) {
try {
st.close();
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
if (con != null) {
try {
con.close();
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
}

// 更新数据库
public static void update(String sql, Object[] params) {
Connection con = JDBCUtils.getConnection();
Statement stmt = null;
ResultSet rs = null;
try {
PreparedStatement ps = con.prepareStatement(sql);
ParameterMetaData psm = ps.getParameterMetaData();// 获得查询语句的元数据信息
int paramNum = psm.getParameterCount();// 得到参数的总个数
for (int i = 1; i <= paramNum; i++) {
ps.setObject(i, params[i - 1]);
}
ps.executeUpdate();
} catch (SQLException e) {
throw new RuntimeException(e);
} finally {
JDBCUtils.colse(rs, stmt, con);
}
}

// 查询数据库
public static Object query(String sql, Object[] params, ResultSetHander rsh) {
Connection con = JDBCUtils.getConnection();
Statement stmt = null;
ResultSet rs = null;
try {
PreparedStatement ps = con.prepareStatement(sql);
ParameterMetaData psm = ps.getParameterMetaData();// 获得查询语句的元数据信息
int paramNum = psm.getParameterCount();// 得到参数的总个数
for (int i = 1; i <= paramNum; i++) {
ps.setObject(i, params[i - 1]);
}
rs = ps.executeQuery();
return rsh.hander(rs);
} catch (SQLException e) {
throw new RuntimeException(e);
} finally {
JDBCUtils.colse(rs, stmt, con);
}
}
}

package cn.itcast;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import org.junit.Test;

/**
* 类说明：数据库操作类
*
* @author 作者: LiuJunGuang
* @version 创建时间：2011-11-6 下午12:02:36
*/
public class JDBCUtilsTest {
@Test
public void find() {
String sql = "select * from history";

JDBCUtils.query(sql, null, new ResultSetHander() {
@Override
public Object hander(ResultSet rs) {
try {
while (rs.next()) {
System.out.println(rs.getString("username"));
}
} catch (SQLException e) {
e.printStackTrace();
}
return null;
}
});
}

@Test
public void update() {
String sql = "delete from history where id = ?";
Object obj[] = { 1 };
JDBCUtils.update(sql, obj);
}

@Test
public void find2() {
Connection con = JDBCUtils.getConnection();
PreparedStatement st = null;
ResultSet rs = null;
try {
String find = "select * from history where username=? and action=?";
st = con.prepareStatement(find);
st.setString(1, "nihao");
st.setString(2, "微笑着");
rs = st.executeQuery();
while (rs.next()) {
System.out.println(rs.getString("username"));
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
JDBCUtils.colse(rs, st, con);
}
}
}