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From Christian Essl <christiane...@yahoo.de>
Subject Re: [HiveMind] Question about DAO creation
Date Fri, 03 Oct 2003 14:45:42 GMT
Sorry I wrote my answer send it and than just saw that Harish was faster 
(and better). Maybe the only thing you should keep from my anser that you 
should shutdown the registry (the pool may need it, because HiveMind now 
supports a shut-down event).

On Fri, 03 Oct 2003 10:12:37 -0400, Harish Krishnaswamy 
<hkrishnaswamy@comcast.net> wrote:

> Here's what I have done in my project, I am using iBatisDB and I love it, 
> I suppose you can do the same with JDBC too.
>
> I have a super DataAccessService...
>
> public class DataAccessServiceImpl implements DataAccessService, 
> Initializable
> {
> // This will be a configuration provided in the module descriptor
> // In JDBC, this will probably be the JNDI path to the DataSource
> public void setResourcePath(String path)
> {
> _resourcePath = path;
> }
>
> // This is used to build the SqlMap, kind of registry for all sql 
> statements.
> // In a plain JDBC env, this is probably where I would get the DataSource 
> (from JNDI typically) and store it locally.
> public void initializeService(Object service)
> {
> try
> {
> Reader reader = Resources.getResourceAsReader(_resourcePath);
> _sqlMap = XmlSqlMapBuilder.buildSqlMap(reader);
> reader.close();
> }
> catch (Exception ex)
> {
> throw new ApplicationRuntimeException("Error Initializing DAS :" + ex);
> }
> }
>
> // Generic statement executions
> public List getList(String statementName, Object parameterObject) throws 
> DaoException
> {
> // executeQuery()
> }
>
> public Object getObject(String statementName, Object parameterObject) 
> throws DaoException
> {
> // executeQuery()
> }
>
> public int update(String statementName, Object parameterObject) throws 
> DaoException
> {
> // executeUpdate()
> }
> }
>
> And I have other DataAccess services compose the super DataAccessService 
> which will be provided by HiveMind as specified in the module descriptor.
>
> For example...
>
> public class ClientDASImpl implements ClientDAS
> {
> private DataAccessService _das;
> public void setDataAccessService(DataAccessService das)
> {
> _das = das;
> }
> public List getClients()
> {
> List list = null;
> try
> {
> list = _das.getList("getClients", new Client());
> }
> catch (DaoException e)
> {
> throw new ApplicationRuntimeException(e);
> }
> return list;
> }
> }
>
> And what I store in the Global is just the registry. That's one thing I 
> noticed in your code, you seem to be building the registry eveytime a 
> service is requested. Here my Global...
>
> public class Global
> {
> private Registry _registry;
>
> public Global()
> {
> ClassResolver resolver = new DefaultClassResolver();
> RegistryBuilder builder = new RegistryBuilder();
>
> builder.processModules(resolver);
>
> _registry = builder.constructRegistry(Locale.getDefault());
> }
>
> public LookupService getLookupService()
> {
> return (LookupService) _registry.getService(ServiceTokens.LOOKUP, 
> LookupService.class);
> }
> ...
> }
>
> I use DBCP for DB connection pooling, that way you externalize all the 
> connection stuff out of the service.
>
> I hope this will be helpful. If you need more info, I will be glad to 
> provide what ever I can.
>
> -Harish
>
>
> Bill Lear wrote:
>
>> I've been using hivemind to build a DAO factory.  I think I may be
>> using this in a rather crude way that undoes some of the good hivemind
>> has done, so I thought I'd ask for some advice.  I have a second 
>> question
>> regarding JDBC connections.
>>
>> First, in Tapestry, I store my DAO object in the Global class, but
>> I seem to have reverted to the singleton pattern instead of
>> doing things the hivemind way:
>>
>> public class Global {
>> private static DAO dao;
>>
>> private static Object daoMutex = new Object();
>>
>> public DAO getDAO() throws DAOException {
>> synchronized (daoMutex) {
>> if (dao == null) {
>> dao = createDAO();
>> }
>> }
>> return dao;
>> }
>>
>> private DAO createDAO() throws DAOException {
>> DAOFactory f = (DAOFactory) Services.getService(DAOFactory.class);
>> return f.createDAO();
>> }
>> }
>>
>> Services is a wrapper around Hivemind that gets a service based on a
>> class name:
>>
>> public class Services {
>> public static Object getService(Class theClass) {
>> ClassResolver resolver = new DefaultClassResolver();
>> RegistryBuilder builder = new RegistryBuilder();
>>
>> builder.processModules(resolver);
>>
>> Registry registry = builder.constructRegistry(Locale.getDefault());
>>
>> return registry.getService(theClass.getName(), theClass);
>> }
>> }
>>
>> My hivemodule looks like this:
>>
>> <module id="com.foobar.eci.dao" version="1.0.0">
>> <service-point id="DAOFactory"
>> interface="com.foobar.eci.dao.DAOFactory">
>> <invoke-factory service-id="hivemind.BuilderFactory">
>> <construct
>> 	        class="com.foobar.eci.dao.mysql.MySQLDAOFactory">
>> <set property="name" value="eci"/>
>> <set property="protocol" value="mysql"/>
>> <set property="driver"
>> 		     value="org.gjt.mm.mysql.Driver"/>
>> <set property="host" value="localhost"/>
>> <set property="port" value="3906"/>
>> <set property="user" value="bogon"/>
>> <set property="password" value="foobar"/>
>> </construct>
>> </invoke-factory>
>> </service-point>
>> </module>
>>
>> I'm not quite sure how to have hivemind construct both the Global
>> object and DAO object, and set the DAO object in the Global object.
>>
>>
>> Second question: I use a command pattern to separate the implementation 
>> of
>> different methods in the DAO class.  So, if I have a DAO that looks like
>> this:
>>
>> public interface DAO {
>> Employee getEmployee(Integer employeeID) throws DAOException;
>>
>> Employee[] getEmployees(String sortColumn) throws DAOException;
>>
>> void insertEmployee(Employee employee) throws DAOException;
>> }
>>
>> I implement this with a class to expose this interface, and three
>> classes to implement each of the commands.  Notice the MySQLDAO
>> class stores the JDBC connection object and passes it to each
>> of the command classes it constructs:
>>
>> public class MySQLDAO implements DAO {
>> void init(Connection connection) throws DAOException {
>> try {
>> getEmployee = new GetEmployee(connection);
>> getEmployees = new GetEmployees(connection);
>> insertEmployee = new InsertEmployee(connection);
>> } catch (SQLException sex) {
>> LOG.error(sex.toString());
>> throw new DAOException(sex.toString());
>> }
>> }
>>
>> private GetEmployee getEmployee;
>>
>> public Employee getEmployee(Integer employeeID) throws DAOException {
>> return getEmployee.execute(employeeID);
>> }
>>
>> private GetEmployees getEmployees;
>>
>> public Employee[] getEmployees(String sortColumn) throws DAOException {
>> return getEmployees.execute(sortColumn);
>> }
>>
>> private InsertEmployee insertEmployee;
>>
>> public void insertEmployee(Employee employee) throws DAOException {
>> insertEmployee.execute(employee);
>> }
>> }
>>
>> The factory is what I have Hivemind creating:
>>
>> public class MySQLDAOFactory implements DAOFactory {
>> private String name;
>> private String protocol;
>> private String driver;
>> private String host;
>> private String port;
>> private String user;
>> private String password;
>>
>> public DAO createDAO() throws DAOException {
>> MySQLDAO dao = new MySQLDAO();
>>
>> try {
>> String connURL = "jdbc:" + protocol + "://";
>>
>> if (host.length() == 0) {
>> connURL += name;
>> } else {
>> connURL += host + ":" + port + "/" + name;
>> }
>>
>> // This ensures no timeouts for MySQL after default idle period
>> connURL += "?autoReconnect=true";
>>
>> Class.forName(driver);
>> dao.init(DriverManager.getConnection(connURL, user, password));
>> } catch (SQLException sex) {
>> throw new DAOException(sex);
>> } catch (ClassNotFoundException ex) {
>> throw new DAOException(ex);
>> }
>>
>> return dao;
>> }
>>
>> // Get-Set methods for private variables elided ...
>> }
>>
>> So, what I'm wondering is: I have embedded a JDBC connection object in
>> the each of the three command objects.  This seems too direct and
>> inflexible, but I don't know what other alternatives to use.  Also, I
>> would like to be able to unit-test each of the three command classes,
>> but I would prefer to be able to use hivemind to construct the JDBC
>> connection for me, in which case, I might re-factor things in the
>> MySQLDAO class itself to also take advantage of hivemind to get the
>> connection object (but then, what about pooling?  Can hivemind create
>> a JDBC connection?  Is this desirable?).
>>
>> Finally, when testing the DAO, I need to be able to clear the database
>> before each test case method is run.  I would prefer to use the same
>> connection that the DAO has, but exposing that in the DAO interface
>> seems a bit lame (Connection getConnection()) and too concrete.
>>
>> In any case, if anyone has comments or suggestions to share on managing
>> JDBC connections, I'd appreciate it.
>>
>>
>> Bill
>>
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>>
>>
>>
>
>
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