ad_qqread_mid_big">
　　六.范例代码
　
　　1.实现数据访问对象模式

　　范例9-4时表示customer信息的持久性对象的dao范例代码。当findcustomer()被调用时，cloudscapecustomerdao创建一个customer值对象。

　　范例9-6是使用dao的范例代码。

　　2.实现数据访问对象的工厂策略

　　1)使用工厂方法模式

　　2)使用抽象工厂模式

　　范例代码9-2是cloudscapedaofactory的范例代码。

　　范例代码9-3中的customerdao接口为customer持久性对象定义了dao方法，这些接口是被所有具体dao实现来实现的，比如cloudscapecustomerdao、oraclecustomerdao、已经sybasecustomerdao。account和orederdao接口也与此类似。

　　example 9.1 abstract daofactory class

// abstract class dao factory public abstract class daofactory { 　// list of dao types supported by the factory 　public static final int cloudscape = 1; 　public static final int oracle = 2; 　public static final int sybase = 3; 　... 　// there will be a method for each dao that can be 　// created. the concrete factories will have to 　// implement these methods. 　public abstract customerdao getcustomerdao(); 　public abstract accountdao getaccountdao(); 　public abstract orderdao getorderdao(); 　... 　public static daofactory getdaofactory( 　　int whichfactory) { 　 　　　switch (whichfactory) { 　　　　case cloudscape: 　　　　　return new cloudscapedaofactory(); 　　　　case oracle : 　　　　　return new oracledaofactory(); 　　　　case sybase : 　　　　　return new sybasedaofactory(); 　　　　　... 　　　　default : 　　　　　return null; 　　　} 　　} 　}

　　example 9.2 concrete daofactory implementation for cloudscape

// cloudscape concrete dao factory implementation import java.sql.*; public class cloudscapedaofactory extends daofactory { 　public static final string driver="com.cloudscape.core.rmijdbcdriver"; 　public static final string dburl="jdbc:cloudscape:rmi://localhost:1099/corej2eedb"; 　// method to create cloudscape connections 　public static connection createconnection() { 　　// use driver and dburl to create a connection 　　// recommend connection pool implementation/usage 　} 　public customerdao getcustomerdao() { 　　// cloudscapecustomerdao implements customerdao 　　return new cloudscapecustomerdao(); 　} 　public accountdao getaccountdao() { 　　// cloudscapeaccountdao implements accountdao 　　return new cloudscapeaccountdao(); 　} 　public orderdao getorderdao() { 　　// cloudscapeorderdao implements orderdao 　　return new cloudscapeorderdao(); 　} 　... }

　　example 9.3 base dao interface for customer

// interface that all customerdaos must support public interface customerdao { 　public int insertcustomer(...); 　public boolean deletecustomer(...); 　public customer findcustomer(...); 　public boolean updatecustomer(...); 　public rowset selectcustomersrs(...); 　public collection selectcustomersvo(...); 　... }

　　example 9.4 cloudscape dao implementation for customer

// cloudscapecustomerdao implementation of the // customerdao interface. this class can contain all // cloudscape specific code and sql statements. // the client is thus shielded from knowing // these implementation details. import java.sql.*; public class cloudscapecustomerdao implements customerdao { 　public cloudscapecustomerdao() { 　　// initialization 　} 　// the following methods can use 　// cloudscapedaofactory.createconnection() 　// to get a connection as required 　public int insertcustomer(...) { 　　// implement insert customer here. 　　// return newly created customer number 　　// or a -1 on error 　} 　public boolean deletecustomer(...) { 　　// implement delete customer here 　　// return true on success, false on failure 　} 　public customer findcustomer(...) { 　　// implement find a customer here using supplied 　　// argument values as search criteria 　　// return a value object if found, 　　// return null on error or if not found 　} 　public boolean updatecustomer(...) { 　　// implement update record here using data 　　// from the customerdata value object 　　// return true on success, false on failure or 　　// error 　} 　public rowset selectcustomersrs(...) { 　　// implement search customers here using the 　　// supplied criteria. 　　// return a rowset. 　} 　public collection selectcustomersvo(...) { 　　// implement search customers here using the 　　// supplied criteria. 　　// alternatively, implement to return a collection 　　// of value objects. 　} 　... }

　　example 9.5 customer value object

public class customer implements java.io.serializable { 　// member variables 　int customernumber; 　string name; 　string streetaddress; 　string city; 　... 　// getter and setter methods... 　... }

　　example 9.6 using a dao and dao factory ?client code

... // create the required dao factory daofactory cloudscapefactory = daofactory.getdaofactory(daofactory.daocloudscape); // create a dao customerdao custdao = cloudscapefactory.getcustomerdao(); // create a new customer int newcustno = custdao.insertcustomer(...); // find a customer object. get the value object. customer cust = custdao.findcustomer(...); // modify the values in the value object. cust.setaddress(...); cust.setemail(...); // update the customer object using the dao custdao.updatecustomer(cust); // delete a customer object custdao.deletecustomer(...); // select all customers in the same city customer criteria=new customer(); criteria.setcity("广州"); collection customerslist = custdao.selectcustomersvo(criteria); // returns customerslist - collection of customer // value objects. iterate through this collection to // get values. ...

>>>更多专题请看java对象专题