1_基础版JDBC-DBHelper扩展(事务及大数据操作)

JDBC - 基础版DBHelper

/MyProperties.java/

public class MyProperties extends Properties{

private static MyProperties myproperties;

private MyProperties(){

InputStream iis = MyProperties.class.getClassLoader().getResourceAsStream(“db.properties”);

try{

super.load( iis );

}catch( IOException e ){

e.printStackTrace();

}

}

public static MyProperties getInstance(){
if( myproperties == null ){
myproperties = new MyProperties();
}
return myproperties;
}

}

/[b]****************************************************************[/b]/

/DBHelper.java/

public class DBHelper{

// 静态块 , 读取一次数据库驱动,
static{
try{
Class.forName( MyProperties.getInstance().getProperty("driver") );
}catch( ClassNotFoundException e ){
e.printStackTrace();
}
}

//获取数据库联接
public Connection getCon() throws SQLException {
MyProperties mp = MyProperties.getInstance();
Connection con = DriverManager.getConnection( mp.getProperty("url") ,
mp.getProperty ("username") , mp.getProperty("password") );
return con;
}

//查询
public List<Map<String , String >> findAll( String sql ,List<Object> params )throws SQLException{
Connection con = getCon();
PreparedStatement pstmt = con.prepareStatement( sql );
setParams( pstmt , params );
ResultSet rs = pstmt.executeQuery();
ResultSetMetaData rsmd = rs.getMetaData(); //获取关于 ResultSet 对象中列的类型和属性信息的对象

List<String> cnlist = new ArrayList<String>();
for( int i = 1; i <= rsmd.getColumnCount() ; i++ ){
cnlist.add( rsmd.getColumnName( i ) );
}

List<Map<String , String >> list = new ArrayList<Map<String ,String >>();
while( rs.next() ){
Map<String , String > map = new HashMap<String , String >();
for( String cn :cnlist ){
map.put( cn , rs.getString(cn) );
}
list.add( map );
}
closeAll(pstmt ,con ,rs );
return list;
}

//查询聚合函数
public double findDouble( String sql , List<Object> params ) throws SQLException{
double result = 0;
Connection con = getCon();
PreparedStatement pstmt = con.prepareStatement( sql );
setParams( pstmt ,params );
ResultSet rs = pstmt.executeQuery();
while( rs.next() ){
rs.getDouble( 1 );
}
closeAll( pstmt ,con ,rs );
return result;
}

//封装增删改
public int doUpdate( String sql , List<Object> params ) throws SQLException{
Connection con = getCon();
PreparedStatement pstmt = con.prepareStatement( sql );
setParams( pstmt ,params );
int result = pstmt.executeUpdate();
closeAll( pstmt ,con ,null );
return result;
}

//封装带事务的增删改
public void doUpdateTran( List<String> sqls ,List< List<Object> > listparams ){
Connection con = getCon();
PreparedStatement pstmt = null;
con.setAutoCommit( false );  //关闭隐式事务( 一句SQL语句提交一次 )
try{
if( sqls != null && sqls.size() > 0 ){
for( int i = 0; i < sqls.size() ; i++ ){
String sql = sqls.get( i );     // 取出每一条sql语句.
pstmt = con.prepareStatement( sql );
setParams( pstmt , listparams( i ) );
pstmt.executeUpdate();
}
}
con.commit();
}catch( Exception e ){
if( con != null ){
con.rollback;   // 回滚
}
}finally{
con.setAutoCommit( true );  //恢复隐式事务
closeAll( pstmt ,con ,null );
}

}

//大数据的操作 , 批处理
// 集合嵌套集合.
public void doBigDataUpdate( String sql , List<List<Object>> params ) throws SQLException{
Connection con = getCon();
con.setAutoCommit( false );
PreparedStatement pstmt = null;
try{
pstmt = con.prepareStatement( sql );
for( int i = 0; i < params.size() ; i++ ){
List<Object> paramsList = params.get( i );
setParams( pstmt , paramsList );
pstmt.addBatch();   //添加一次预定义参数
if( i % 1000 == 0 ){
pstmt.executeBatch(); //批量执行预定义sql ,这个返回值里面存的是每条语句执行的结果
}
}
pstmt.executeBatch();   // 多余的余数在执行.
con.commit();
}catch( Exception e){
e.printStackTrace();
con.rollback();    // 异常 ====>>>> 回滚。
}finally{
con.setAutoCommit( true );
closeAll( pstmt ,con ,null );
}
}

//设置参数 占位符
private void setParams( PreparedStatement pstmt , List<Object> params ) throws SQLException{
if( params != null && params.size() > 0 ){
for( int i = 1;  i <= params.size() ; i++ ){
pstmt.setObject( i , params.get( i-1 ));
}
}
}

// 释放资源
private sttaic void clossAll( PreparedStatement pstmt , Connection con , ResultSet rs ){
if( pstmt != null ){
pstmt.close();
}
if( con !=null ){
con.close();
}
if( rs != null ){
rs.close();
}
}

}