JDNI数据源的模式

Question

I'm using a JNDI ressource in Tomcat8 for connecting to a MS-SQL database (Azure). Randomly I experience Connection closed exception, eventually preceeded by Connection peer reset events. When this happens, the service is dead (running into Connection closed for every request) and restarting the tomcat (redploying) is the only chance to get it up again.

On my way trying to solve this I double(triple)-checked every method for unclosed connections, I assure that every connection is opened as try-with-ressource .

Currently I'm trying to get a better understanding about JNDI ressources and the connection pooling, I'm asking what is the preferred pattern to implement a service class which is injected into other services. Eg questions are

1. Where should the DataSource be allocated by calling ctx.lookup() ? On method level or class scope? Eg when using the hk2 @Service annotation it seems that a service is instantiated only once and not per request. Currently ctx.lookup() is invoced once (in the constructor) and the DataSource is stored in a class field and later on accessed by the methods using this.dataSource . Does this make sense ? Or should the DataSource be retrieved on every request (=method call)

2. How can I verify the execution of several options of the DataSource, eg testOnBorrow and removeAbandoned (see complete configuration below) are executed correctly? There is an option logAbandoned but I can not see anything in my logs. Where should this appear anyhow? Can I somehow specifiy a certain log level for the pool? I only found org.apache.tomcat.jdbc.pool , but this class seems only to be called when creating the pool (at least this is the only moment when logs appear, even on level FINEST ).

3. Are there general patterns which I'm not aware of?

Here my current configuration:

<Resource name="jdbc/mssql"
          auth="Container"
          type="javax.sql.XADataSource"
          driverClassName="com.microsoft.sqlserver.jdbc.SQLServerDriver"
          username="***"
          password="***"
          url="jdbc:sqlserver://***.database.windows.net:1433;database=***;encrypt=true;trustServerCertificate=false;hostNameInCertificate=*.database.windows.net;loginTimeout=30;"
          factory="org.apache.tomcat.jdbc.pool.DataSourceFactory"
          removeAbandonedOnBorrow="true"
          removeAbandonedTimeout="55"
          removeAbandonedOnMaintenance="true"
          timeBetweenEvictionRunsMillis="34000"
          minEvictableIdleTimeMillis="55000"
          logAbandoned="true"
          validationQuery="SELECT 1"
          validationInterval="34000"
        />

Thx, gapvision

Answer 1

Gapvision, you can check this link - What is the good design pattern for connection pooling?

Probably, you would want to go with the object pool pattern. Hope this helps !!

Answer 2

I'm asking what is the preferred pattern to implement a service class which is injected into other services.

Try spring data. It is very helpful in organizing resources to access data.

Without spring, without tomcat built-in features, you indeed need create your own singletons to allocate DataSource or ConnectionPool.

Without spring(assuming you build web app for tomcat), you can add to web.xml:

<resource-ref>
<description>H2DB</description>
<res-ref-name>jdbc/project1</res-ref-name>
<res-type>javax.sql.DataSource</res-type>
<res-auth>Container</res-auth>
</resource-ref>

And in context.xml of tomcat:

<Resource name="jdbc/project1" auth="Container" type="javax.sql.DataSource" driverClassName="org.h2.Driver"  url="jdbc:h2:tcp://localhost/~/project1"   username="sa" password="" maxActive="20" maxIdle="10" maxWait="-1"/>

And then you can lookup data source in each request:

Context ctx = new InitialContext();
Context envContext = (Context) ctx.lookup("java:comp/env");
DataSource ds = (DataSource) envContext.lookup("jdbc/project1");
Connection conn = null;
try {
conn = ds.getConnection();
PreparedStatement ps = conn.prepareStatement("INSERT INTO USERS (NAME) VALUES (?)");
ps.setString(1,name);
ps.executeUpdate();
response.getWriter().write("added user "+name);
response.getWriter().write("\n");
} finally {
if (conn!=null) { conn.close(); }
}

Or you can create a singleton class and lookup DataSource once , on start or lazy, as singletons do.

But better try spring data.