java操作数据库—SqlHelper（读取properties文件）

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连接mysql数据库：

mysql.properties：

url=jdbc:mysql://127.0.0.1/test
username=root
driver=com.mysql.jdbc.Driver
password=123456

SqlHelper.java 工具类：

public class SqlHelper

{
//定义变量
private static Connection ct = null;
//大多数情况下用preparedstatement替代statement
private static PreparedStatement ps = null;
private static ResultSet rs = null;

//连接数据库的参数
private static String url = "";
private static String username = "";
private static String driver = "";
private static String passwd = "";

private static CallableStatement cs = null;
public static CallableStatement getCs()
{
return cs;
}
private static Properties pp = null;
private static InputStream fis = null;
//加载驱动，只需要一次，用静态代码块
static
{
try
{
//从dbinfo.properties
pp = new Properties();
fis=SqlHelper.class.getClassLoader().getResourceAsStream("mysql.properties");//mysql.properties放在src同目录下
pp.load(fis);
url = pp.getProperty("url");
username = pp.getProperty("username");
driver = pp.getProperty("driver");
passwd = pp.getProperty("password");

Class.forName(driver);
}
catch (Exception e)
{
e.printStackTrace();
}
finally
{
try
{ fis.close();}
catch(IOException e) {e.printStackTrace();}
fis = null;//垃圾回收站上收拾
}

}
//得到连接
public static Connection getConnection()
{
try
{ct = DriverManager.getConnection(url,username,passwd);}
catch(Exception e) {e.printStackTrace();}
return ct;
}

public static ResultSet executeQuery(String sql,String[] parameters)
{
try
{
ct=getConnection();
ps=ct.prepareStatement(sql);
if(parameters!=null)
{
for(int i=0;i<parameters.length;i++)
{
ps.setString(i+1,parameters[i]);
}
}
rs = ps.executeQuery();
}
catch(Exception e)
{
e.printStackTrace();
throw new RuntimeException(e.getMessage());
}
finally
{

}
return rs;
}

public static Connection getCt()
{
return ct;
}
public static PreparedStatement getPs()
{
return ps;
}
public static ResultSet getRs()
{
return rs;
}

public static void executeUpdate2(String[] sql,String[][] parameters)
{
try
{
ct = getConnection();
ct.setAutoCommit(false);

for(int i=0;i<sql.length;i++)
{

if(null!=parameters[i])
{
ps = ct.prepareStatement(sql[i]);
for(int j=0;j<parameters[i].length;j++)
{
ps.setString(j+1,parameters[i][j]);
}
ps.executeUpdate();
}

}

ct.commit();

}catch (Exception e)
{
e.printStackTrace();
try
{
ct.rollback();
}
catch (SQLException e1)
{
e1.printStackTrace();
}
throw new RuntimeException(e.getMessage());
}finally
{
close(rs,ps,ct);
}

}

//先写一个update、delete、insert
//sql格式：update 表名 set 字段名 =？where 字段=？
//parameter神应该是（”abc“,23）
public static void executeUpdate(String sql,String[] parameters)
{
try
{
ct=getConnection();
ps = ct.prepareStatement(sql);
if(parameters!=null)
{
for(int i=0;i<parameters.length;i++)
{
ps.setString(i+1,parameters[i]);
}

}
ps.executeUpdate();
}
catch(Exception e)
{
e.printStackTrace();//开发阶段
//抛出异常
//可以处理，也可以不处理
throw new RuntimeException(e.getMessage());
}
finally
{
close(rs,ps,ct);
}
}

public static void close(ResultSet rs,Statement ps,Connection ct)
{
//关闭资源(先开后关)
if(rs!=null)
{
try
{
rs.close();
}
catch(SQLException e)
{
e.printStackTrace();
}
rs=null;
}
if(ps!=null)
{
try
{
ps.close();
}
catch(SQLException e)
{
e.printStackTrace();
}
ps=null;
}
if(null!=ct)
{
try
{
ct.close();
}
catch(SQLException e)
{
e.printStackTrace();
}
ct=null;
}
}
}

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