java分享第十七天-03（封装操作mysql类）

import java.sql.*;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import com.mysql.jdbc.Connection;
import com.mysql.jdbc.Statement;
public class ConnectMySQL {
public static String driver = "com.mysql.jdbc.Driver";
private static String host;
private static String user;
private static String pwd;
private static Connection conn = null;
private static Statement stmt = null;
public static void connect(String host, String user, String pwd) {
ConnectMySQL.close();
ConnectMySQL.host = host;
ConnectMySQL.user = user;
ConnectMySQL.pwd = pwd;
}
public static synchronized List<HashMap<String, String>> query(String sql) {
return ConnectMySQL.result(sql);
}
public static synchronized void close() {
try {
if (stmt != null) {
stmt.close();
stmt = null;
}
if (conn != null) {
conn.close();
conn = null;
}
} catch (SQLException e) {
e.printStackTrace();
}
}
private static void connectMySQL() {
try {
Class.forName(driver).newInstance();
conn = (Connection) DriverManager.getConnection("jdbc:mysql://"
+ host + "?useUnicode=true&characterEncoding=UTF8", user,
pwd);
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
}
private static void statement() {
if (conn == null) {
ConnectMySQL.connectMySQL();
}
try {
stmt = (Statement) conn.createStatement();
} catch (SQLException e) {
e.printStackTrace();
}
}
private static ResultSet resultSet(String sql) {
ResultSet rs = null;
if (stmt == null) {
ConnectMySQL.statement();
}
try {
rs = stmt.executeQuery(sql);
} catch (SQLException e) {
e.printStackTrace();
}
return rs;
}
private static List<HashMap<String, String>> result(String sql) {
ResultSet rs = ConnectMySQL.resultSet(sql);
List<HashMap<String, String>> result = new ArrayList<HashMap<String, String>>();
try {
ResultSetMetaData md = rs.getMetaData();
int cc = md.getColumnCount();
while (rs.next()) {
HashMap<String, String> columnMap = new HashMap<String, String>();
for (int i = 1; i <= cc; i++) {
columnMap.put(md.getColumnName(i), rs.getString(i));
}
result.add(columnMap);
}
} catch (SQLException e) {
e.printStackTrace();
}
return result;
}
public static void main(String[] args) throws SQLException {
ConnectMySQL
.connect("192.168.1.1/test", "test", "test");
List<HashMap<String, String>> rs = ConnectMySQL
.query("SELECT * from test");
System.out.println(rs.get(0).get("test"));
ConnectMySQL.close();
}
}