Metadata meta data

First, the basic

Definition: A description of the database, table, and column-related information.
When to use: use when you want to get information about a database.
One "database meta-data-through DatabaseMetaData
DatabaseMetaData Dbmd = Conn.getdatabasemetadata ();
Code

Connection conn =c3p0utils.getmysqlconnection (); //get database meta-data ———— DatabaseMetaDataDatabaseMetaData Dbmd =Conn.getmetadata (); String Driver=Dbmd.getdrivername (); System.out.println ("DriverName:" + driver);//mysql-ab JDBC DriverString URL =Dbmd.geturl (); System.out.println ("URL:" + URL);//Jdbc:mysql://127.0.0.1:3306/jdbc            intLevel = Dbmd.getdefaulttransactionisolation ();//To get the transaction level, the level of the value can have the field value of the Connectin class to viewSystem.out.println ("Level:" + level);//2String ProductName =Dbmd.getdatabaseproductname (); System.out.println ("ProductName:" + productName);//MySQL

     Two "parameter metadata-via Parametermetadata
             Parametermetadata PMD = pstmt.getparametermetadata;
        code:

           Connection conn = c3p0utils.getmysqlconnection ();             = Conn.preparestatement (Sqlmapping.query_inf); // SELECT * from jdbc.test_batch WHERE id =?             // get parameter metadata            Parametermetadata PMD = pstmt.getparametermetadata ();             int cnt = pmd.getparametercount ();            System.out.println ("Total" + cnt + "parameters"); // The public parameter, which is the SQL statement?  The number, here is 1

Three "result set data elements--by ResultSetMetaData
ResultSetMetaData RSMD = Rs.getmetadata ();
Code

String SQL = "SELECT * FROM Jdbc.test_batch"; Connection Conn=c3p0utils.getmysqlconnection (); PreparedStatement pstmt=conn.preparestatement (SQL); ResultSet RS=Pstmt.executequery (); ResultSetMetaData RSMD=Rs.getmetadata (); intCNT = Rsmd.getcolumncount ();//number of result sets             for(inti = 1; I <= CNT; i++) {String colname= Rsmd.getcolumnname (i);//get the name of each columnSystem.out.println ("colname =" + colname);//colname = id colname = Name colname = Age}

Summarize:
The core rules are as follows:
ResultSetMetaData Resultset.getmetadata ();
Parametermetadata Psmt.getmetadata ();
DatabaseMetaData Conn.getmetadata ();

Second, using metadata meta-data optimization cud operation and R operation (packaged into tools for easy use)
One "cud operation
Code

        //cud Operation         Public Static intUpdate (String sql, object[] params)throwsSQLException {Connection conn=c3p0utils.getmysqlconnection (); PreparedStatement pstmt= conn.preparestatement (SQL);//INSERT into Meta.user (username,salary) VALUES (?,?) //Get parameter MetadataParametermetadata PMD =Pstmt.getparametermetadata (); //number of parameters obtained            intSize =Pmd.getparametercount (); //the value of the loop-bound object             for(inti = 0; i < size; i++) {Pstmt.setobject (i+ 1, Params[i]); }            introws =pstmt.executeupdate ();            C3p0utils.close (conn); returnrows; }    

Two "R operation
Code

        //R operation (requires: the name of the JavaBean must be the same as the name of the database field)         Public Static<T> list<t> query (String sql, object[] params, Class clazz)throwsSQLException, Instantiationexception, Illegalaccessexception, invocationtargetexception {Connection conn =c3p0utils.getmysqlconnection (); List<T> list =NewArraylist<t>(); PreparedStatement pstmt= conn.preparestatement (SQL);//SELECT * from meta.user WHERE id =?Parametermetadata PMD =Pstmt.getparametermetadata (); intCNT =Pmd.getparametercount ();  for(inti = 0; I < CNT; i++) {Pstmt.setobject (i+1, Params[i]); } ResultSet RS=Pstmt.executequery ();  while(Rs.next ()) {ResultSetMetaData Rsmd=Rs.getmetadata (); intColumn =Rsmd.getcolumncount (); T T=(T) clazz.newinstance ();  for(inti = 0; I < column; i++) {String colname= Rsmd.getcolumnname (i+1);                Beanutils.setproperty (t, ColName, Rs.getobject (colname));            } list.add (t); }

C3p0utils.closeall (conn, pstmt, RS);

return list;
}

Metadata meta data