java常用sql处理函数类

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.HashMap;

//封装了数据库的增删改查操作

public class Sqlutil {
/**
* 连接数据库
* @param url
* @param user
* @param passwd
* @return
*/
public static Connection connect(String url, String user, String passwd) {
Connection conn = null;
try {
Class.forName("com.mysql.jdbc.Driver");
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
conn = DriverManager.getConnection(url, user, passwd);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return conn;
}

/**
*   查一条
* @param conn
* @param sql
* @return
*/
public static HashMap<String, String> fetchOne(Connection conn, String sql) {
Statement stat = null;
ResultSet res = null;
HashMap<String, String> map = new HashMap<>();
try {
stat = conn.createStatement();
res = stat.executeQuery(sql);
int col = res.getMetaData().getColumnCount();
res.next();
for (int i = 1; i < col; i++) {
map.put(res.getMetaData().getColumnName(i), res.getString(i));
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return map;
}

/**
*   查多条
* @param conn
* @param sql
* @return
*/
public static HashMap<Integer, HashMap<String, String>> fetchAll(Connection conn, String sql) {
Statement stat = null;
ResultSet res = null;
HashMap<Integer,HashMap<String, String>> map = new HashMap<>();
try {
stat = conn.createStatement();
res = stat.executeQuery(sql);
int col = res.getMetaData().getColumnCount();
int j = 0;
while (res.next()) {
HashMap<String, String> tmap = new HashMap<>();
for (int i = 1; i < col; i++) {
tmap.put(res.getMetaData().getColumnName(i), res.getString(i));
}
map.put(j, tmap);
j++;
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return map;
}

/**
*    增删改
* @param conn
* @param sql
* @return
*/
public static int update(Connection conn, String sql) {
Statement stat;
int res = 0;
try {
stat = conn.createStatement();
res = stat.executeUpdate(sql);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return res;
}

}