BaseDao

public class DBHelper {

private static final String DRIVENAME = "com.mysql.jdbc.Driver";
private static final String URL = "jdbc:mysql://192.168.1.200:3306/web";
private static final String USER = "root";
private static final String PASSWORD = "123456";

private Connection conn = null;
private Statement st = null;
private PreparedStatement ppst = null;
private ResultSet rs = null;

/**
* 加载驱动
*/
static{
try {
Class.forName(DRIVENAME).newInstance();
} catch (Exception e) {
System.out.println("驱动加载失败："+e.getMessage());
}
}

/**
* 连接数据库
* @return
*/
public Connection getConn(){
try {
conn = DriverManager.getConnection(URL,USER,PASSWORD);
} catch (SQLException e) {
System.out.println("数据库连接失败："+e.getMessage());
}
return conn;
}


/**
* 获取结果集（无参）
* @param sql
* @return
*/
private ResultSet getRs(String sql){
conn = this.getConn();
try {
st = conn.createStatement();
rs = st.executeQuery(sql);
} catch (SQLException e) {
System.out.println("查询（无参）出错:"+e.getMessage());
}
return rs;
}


/**
* 获取结果集
* @param sql
* @param params
* @return
*/
private ResultSet getRs(String sql,Object[] params){
conn = this.getConn();
try {
ppst = conn.prepareStatement(sql);
if(params!=null){
for(int i = 0;i<params.length;i++){
ppst.setObject(i+1, params[i]);
}
}
rs = ppst.executeQuery();
} catch (SQLException e) {
System.out.println("查询出错："+e.getMessage());
}

return rs;
}


/**
* 查询
* @param sql
* @param params
* @return
*/
public List<Object> query(String sql,Object[] params){

List<Object> list = new ArrayList<Object>();
ResultSet rs = null;
if(params!=null){
rs = getRs(sql, params);
}else{
rs = getRs(sql);
}
ResultSetMetaData rsmd = null;
int columnCount = 0;

try {
rsmd = rs.getMetaData();
columnCount = rsmd.getColumnCount();
while(rs.next()){
Map<String, Object> map = new HashMap<String, Object>();
for(int i = 1;i<=columnCount;i++){
map.put(rsmd.getColumnLabel(i), rs.getObject(i));
}
list.add(map);
}
} catch (SQLException e) {
System.out.println("结果集解析出错："+e.getMessage());
} finally {
closeConn();
}
return list;
}


/**
* 更新（无参）
* @param sql
*/
public int update(String sql){
int affectedLine = 0;//受影响的行数
conn = this.getConn();
try {
st = conn.createStatement();
affectedLine = st.executeUpdate(sql);
} catch (SQLException e) {
System.out.println("更新（无参）失败："+e.getMessage());
} finally {
closeConn();
}
return affectedLine;
}


/**
* 更新
* @param sql
* @param params
* @return
*/
public int update(String sql,Object[] params){
int affectedLine = 0;//受影响的行数
conn = this.getConn();
try {
ppst = conn.prepareStatement(sql);
if(params!=null){
for(int i = 0;i<params.length;i++){
ppst.setObject(i+1, params[i]);
}
}
affectedLine = ppst.executeUpdate();
} catch (SQLException e) {
System.out.println("更新失败："+e.getMessage());
} finally {
closeConn();
}
return affectedLine;
}


private void closeConn(){

if(rs!=null){
try {
rs.close();
} catch (SQLException e) {
System.out.println(e.getMessage());
}
}

if(st!=null){
try {
st.close();
} catch (SQLException e) {
System.out.println(e.getMessage());
}
}

if(ppst!=null){
try {
ppst.close();
} catch (SQLException e) {
System.out.println(e.getMessage());
}
}

if(conn!=null){
try {
conn.close();
} catch (SQLException e) {
System.out.println(e.getMessage());
}
}
}

}