I'm developing a web application at the moment. The web application needs to access a Patients database, which for now is a simple MySQL database but may likely be replaced by some other DB (or data source) in the future. At the moment, everything is hardcoded but I would like to have some way to configure the DB connection (that is, the database URL, user, password etc.).
What would be a simple and straightforward solution? It would be good if I could change the configuration by simple editing of a file.
I've seen there's the Properties API as well as Preferences. Or is there some idiom concerning servlets/web apps?
A servlet is part of a web app, and this web app is deployed in a Java EE container (Tomcat, WebLogic, etc.).
The standard way to get a database connection is to use JNDI to get a DataSource instance, and to ask a connection to this DataSource. The DataSource, most of the time, will pool database connections to avoid creating and closing too many connections and thus be much faster :
Context initCtx = new InitialContext();
DataSource dataSource = (DataSource) initCtx.lookup("java:comp/env/jdbc/MyDataSource");
Connection c = dataSource.getConnection();
try {
// ...
}
finally {
c.close(); // makes the connection available for a new thread
}
The DataSource will have to be declared in the web.xml file:
<resource-ref>
<description>Datasource example</description>
<res-ref-name>jdbc/MyDataSource</res-ref-name>
<res-type>javax.sql.DataSource</res-type>
<res-auth>Container</res-auth>
</resource-ref>
It will have to be defined (with its URL, number of connections, user, password, settings, etc.) inside your Java EE container. This is where it depends on your container.
Read the following explanations for Tomcat : http://tomcat.apache.org/tomcat-7.0-doc/jndi-datasource-examples-howto.html
I think a configuration XML along with your web application is a good idea. Each time the application is initiated by a new request the configuration is loaded and the database connection information available from any internal context that you make.
On IIS this is a standard way through the Web.config file.
regards
Related
We are planning an application using EJB, JPA (persistence) & JSF (Primefaces) architecture on JBoss EAP 6.4. The way data is stored in the database or the nature of the application is, we need to use/implement Role Based Security from application layer as well. We are able to create multiple DB Connection pools (to the same DB instance) in JBoss container and each JNDI is associated with a specific DB role. In other words, if I use JNDI_Role1 connection then it will return rows from DB table according to Role1 vs if I use JNDI_Role2 connection then it will return rows from the same DB table according to Role2 which would be different then Role1 and so on. We have 4 different roles created in DB, so 4 different JNDI connection pools in JBoss container.
Now, can I implement this in my Persistence layer? If yes, how can I do that? Should I create multiple EntityManager instances tied to each connection pool/JNDI? Any suggestions with some sample code would be really appreciated!!
Thanks in advance!!
There are some links which describes role based security: See the links
[1]https://access.redhat.com/documentation/en-US/JBoss_Enterprise_Application_Platform/6.4/html-single/Security_Guide/index.html
[2]https://access.redhat.com/documentation/en-us/red_hat_jboss_enterprise_application_platform/6.4/html-single/how_to_configure_server_security/
[3]https://access.redhat.com/documentation/en-us/red_hat_jboss_enterprise_application_platform/6.4/html-single/security_architecture/#role_based_access_control
I use "Liberty for Java" app and Statica service(Proxy) on Bluemix.
We set http.proxyHost/http.proxyPort/https.proxyHost/https.proxyPort as system properties in Java code every transactions.
for example:
URL url = new URL(xxx);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
........
System.setProperty("http.proxyHost", host);
System.setProperty("http.proxyPort", port);
System.setProperty("https.proxyHost", host);
System.setProperty("https.proxyPort", port);
........
DataOutputStream out = new DataOutputStream(connection.getOutputStream());
I have an issue that one transaction go from the app to a target server directly in spite of tens of thousands of transactions passed the proxy.
Question 1:
Do "Liberty for Java" app on Bluemix clear or update system properties, http.proxyHost/http.proxyPort/https.proxyHost/https.proxyPort?
I wonder "Liberty for Java" app updated with null to access outer servers in multi-thread environment.
Question 2:
Do "Liberty for Java" app on Bluemix communicate with outer servers?
I found the following log in Statica.
https://xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx.agents.na.apm.ibmserviceengage.com
https://xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx.gateway.prd.na.ca.ibmserviceengage.com
( I masked a part of URL.)
P.S. We will change java code with ProxySelector class or Proxy class.
Re #1: No.
Re #2: Potentially yes. In your case, it seems your app is bound with a Monitoring & Analytics service? If so, a data collector will be installed and will send collected data to remote servers.
What's the reason that you need to set the proxy system properties in your code? Is it because you want some connections to go through the proxy and others not?
If so, then the way you do this is not right because the system proxy setting is a global setting, not a thread-scoped setting. This means if one thread sets the proxy setting, all threads will then use that proxy; if one thread unsets it, all threads will then do direct connections. That may explain why you are intermittently seeing some direct connections. The right way is to use a http client lib that supports proxy as parameters, like https://hc.apache.org/httpcomponents-client-ga/httpclient/apidocs/org/apache/http/client/config/RequestConfig.Builder.html#setProxy%28org.apache.http.HttpHost%29
If you want all connections to go through the http proxy, then you should simply set the JAVA_OPTS environment variable to pass in those system properties, e.g., "-Dhttp.proxyHost=x.x.x.x -Dhttp.proxyPort=xx".
I am trying to create a jdbc connection to a postgresql database. I would like to use a datasource. In the documentation of postgresql is stated that one should not use their own implementations of the datasource, but use the implementations of org.apache.commons.dbcp instead. The SharedPoolDatasource looks perfect to me.
The jdbc driver must be postgresql. Glassfish v3.1 offers the opportunity to create a jdbc connection pool. I would like to use that one, but do not know how to make the connection between the commons datasource implementation and the jdbc driver. When I fill in the document on the glassfish server that particular field blanks out forcing me to use the postgresql datasource implementation.
Is this impossible to achieve or do I have to enter data manually in config files? So far I did not have any luck nor feedback. Exceptions should appear in the server.log, but the server.log currently does not show anything (it did show exceptions deploying jsf and ejb applications).
Should be possible....
1. Create a new JDBC Connection Pool:
2. Choose your desired Datasource Implementation Class:
You'll have to setup the details for databasename, user and password in the additional properties tab.
3. Create a new JDBC Resource:
I want to create an entity class from database. My database would be HSQL and i use file to store the data.
I have no problem to config the connection pool to connect to this database # glassfish The name of the resource which uses the connection pool (HSQL-file) is HSQLJdbcResource:
And no problem to reach this resource from a JSP file, this code works perfectly:
But i do have a problem, when i want to create the entity class from database with the netbeans wizard, because somehow the neatbeans can't find the driver for this :
I have the driver and attached to the project and also i can manage to create the entity class trough std datasource but i want trought glassfish resource, because if dont do the way like this --- the file will be locked because of my JPA which use glassfish resource and connection pool... Vicious Circle, is there any solution for this?
Please check to see if the driver path is correct.
Add the hsql driver in your system class path.
Also, this might be helpful: http://hsqldb.org/doc/guide/ch04.html
I've been working on a web application, deployed on Tomcat 7, which use EclipseLink JPA to handle the persistence layer.
Everything works fine in a test environment but we're having serious issues in the production environment due to a firewall cutting killing inactive connections. Basically if a connection is inactive for a while a firewall the sits between the Tomcat server and the DB server kill it, with the result of leaving "stale" connections in the pool.
The next time that connection is used the code never returns, until it gets a "Connection timed out" SQLException (full ex.getMessage() below).
EL Fine]: 2012-07-13
18:24:39.479--ServerSession(309463268)--Connection(69352859)--Thread(Thread[http-bio-8080-exec-5,5,main])--
MY QUERY REPLACED TO POST IT TO SO [EL Config]: 2012-07-13
18:40:10.229--ServerSession(309463268)--Connection(69352859)--Thread(Thread[http-bio-8080-exec-5,5,main])--disconnect
[EL Info]: 2012-07-13
18:40:10.23--UnitOfWork(1062365884)--Thread(Thread[http-bio-8080-exec-5,5,main])--Communication
failure detected when attempting to perform read query outside of a
transaction. Attempting to retry query. Error was: Exception
[EclipseLink-4002] (Eclipse Persistence Services -
2.3.0.v20110604-r9504): org.eclipse.persistence.exceptions.DatabaseException Internal
Exception: java.sql.SQLException: Eccezione IO: Connection timed out
I already tried several configuration in the persistence.xml, but since I have no access to the firewall configuration I had no luck with these methods. I also tried to use setCheckConnections()
ConnectionPool cp = ((JpaEntityManager)em).getServerSession().getDefaultConnectionPool();
cp.setCheckConnections();
cp.releaseConnection(cp.acquireConnection());
I managed to solve the issue in a test script using testOnBorrow, testWhileIdle and other features that are avalaible from DBCP Apache Commons. I'd like to know how to override the EclipseLink internal connection pool to use a custom connection pool so that I can provide an already configured pool, based on DBCP rather than just configuring the internal one using persistence.xml.
I know I should provide a SessionCustomizer, I'm uncertain which one is the correct pattern to use. Basically I would like to preserve the performance of DBCP in a JPA-like way.
I'm deploying on Tomcat 7, I know that if I switch to GF I won't have this problem, but for a matter of consistency with other webapp on the same server I'd prefere to stay on Tomcat.
What you want is definitely possible, but you might be hitting the limits of the "do it yourself" approach.
This is one of the more difficult things to explain, but there are effectively two ways to configure your EntityManagerFactory. The "do it yourself" approach and the "container" approach.
When you call Persistence.createEntityManagerFactory it eventually delegates to this method of the PersistenceProvider interface implemented by EclipseLink:
EntityManagerFactory createEntityManagerFactory(String emName, Map map)
The deal here is EclipseLink will then take it upon itself to do all the work, including its own connection creation and handling. This is the "do it yourself" approach. I don't know EclipseLink well enough to know if there is a way to feed it connections using this approach. After two days on Stackoverflow it doesn't seem like anyone else has that info either.
So here is why this "works in GF". When you let the container create the EntityManagerFactory for you by having it injected or looking it up, the container uses a different method on the PersistenceProvider interface implemented by EclipseLink:
EntityManagerFactory createContainerEntityManagerFactory(PersistenceUnitInfo info, Map map)
The long and short of it is that this PersistenceUnitInfo is an interface that the container implements and has these two very key methods on it:
public DataSource getJtaDataSource();
public DataSource getNonJtaDataSource();
With this mode EclipseLink will not try to do its own connection handling and will simply call these methods to get the DataSource from the container. This is really what you need.
There are two possible approaches you could take to solving this:
You could attempt to instantiate the EclipseLink PersistenceProvider implementation yourself and call the createContainerEntityManagerFactory method passing in your own implementation of the PersistenceUnitInfo interface and feed the DBCP configured DataSource instances into EclipseLink that way. You would need to parse the persistence.xml file yourself and feed that data in through the PersistenceUnitInfo. As well EclipseLink might also expect a TransactionManager, in which case you'll be stuck unless you hunt down a TransactionManager you can add to Tomcat.
You could use the Java EE 6 certified version of Tomcat, TomEE. DataSources are configured in the tomee.xml, created using DBCP with full support for all the options you need, and passed to the PersistenceProvider using the described createContainerEntityManagerFactory call. You then get the EntityManagerFactory injected via #PersistenceUnit or look it up.
If you do attempt to use TomEE, make sure your persistence.xml is updated to explicitly set transaction-type="RESOURCE_LOCAL" because the default is JTA. Even though it's non-compliant to use JTA with the Persistence.createEntityManagerFactory approach, there aren't any persistence providers that will complain and let you know you're doing something wrong, they treat it as RESOURCE_LOCAL ignoring the schema. So when you go to port your app to an actual certified server, it blows up.
Another note on TomEE is that in the current release, you'll have to put your EclipseLink libs in the <tomcat>/lib/ directory. This is fixed in trunk, just not released yet.
I'm not sure how useful these slides will be without the explanation that goes along with them, but the second part of this presentation is a deep dive into how container-managed EntityManager's work, specifically with regards to connection handling and transactions. You can ignore the transaction part as you aren't using them and already have an in production you're not likely to dramatically change, but it might be interesting for future development.
Best of luck!