We Keep Coding

How to configure JDBC Resource in Embedded Tomcat 8?

I need to set up a connection pool for an application that uses an embedded Tomcat 8 application server. Normally, I would configure a new resource in the context.xml file. But of course, such a file does not exist when using the embedded version. The definition of the resource would look like this:
<Context>
<Resource name="jdbc/dbname" auth="Container" type="javax.sql.DataSource" username="username" password="password" driverClassName="org.postgresql.Driver" description="Database" url="jdbc:postgresql://localhost:5432/dbname" maxActive="20" maxIdle="3" />
</Context>
Therefore, there must be another solution for adding resources to a context. Is it possible to add the data source resource directly to the Standardcontext in code? If yes, how? Or how else can this be done when using the embedded version?

You can write your own factory and integrate it into Tomcat, and then configure the use of this factory in the element for the web application.
1. Write A Resource Factory Class
You must write a class that implements the JNDI service provider javax.naming.spi.ObjectFactory interface. Every time your web application calls lookup() on a context entry that is bound to this factory (assuming that the factory is configured with singleton="false"), the getObjectInstance() method is called.
To create a resource factory that knows how to produce MyBean instances, you might create a class like this:
package com.mycompany;
import java.util.Enumeration;
import java.util.Hashtable;
import javax.naming.Context;
import javax.naming.Name;
import javax.naming.NamingException;
import javax.naming.RefAddr;
import javax.naming.Reference;
import javax.naming.spi.ObjectFactory;
public class MyBeanFactory implements ObjectFactory {
public Object getObjectInstance(Object obj,
Name name2, Context nameCtx, Hashtable environment)
throws NamingException {
// Acquire an instance of our specified bean class
MyBean bean = new MyBean();
// Customize the bean properties from our attributes
Reference ref = (Reference) obj;
Enumeration addrs = ref.getAll();
while (addrs.hasMoreElements()) {
RefAddr addr = (RefAddr) addrs.nextElement();
String name = addr.getType();
String value = (String) addr.getContent();
if (name.equals("foo")) {
bean.setFoo(value);
} else if (name.equals("bar")) {
try {
bean.setBar(Integer.parseInt(value));
} catch (NumberFormatException e) {
throw new NamingException("Invalid 'bar' value " + value);
}
}
}
// Return the customized instance
return (bean);
}
}
In this example, we are unconditionally creating a new instance of the com.mycompany.MyBean class, and populating its properties based on the parameters included in the element that configures this factory (see below). You should note that any parameter named factory should be skipped - that parameter is used to specify the name of the factory class itself (in this case, com.mycompany.MyBeanFactory) rather than a property of the bean being configured.
2. Declare Your Resource Requirements
Next, modify your web application deployment descriptor (/WEB-INF/web.xml) to declare the JNDI name under which you will request new instances of this bean. The simplest approach is to use a element, like this:
<resource-env-ref>
<description>
Object factory for MyBean instances.
</description>
<resource-env-ref-name>
bean/MyBeanFactory
</resource-env-ref-name>
<resource-env-ref-type>
com.mycompany.MyBean
</resource-env-ref-type>
</resource-env-ref>
WARNING - Be sure you respect the element ordering that is required by
the DTD for web application deployment descriptors! See the Servlet
Specification for details.
3. Code Your Application's Use Of This Resource
A typical use of this resource environment reference might look like this:
Context initCtx = new InitialContext();
Context envCtx = (Context) initCtx.lookup("java:comp/env");
MyBean bean = (MyBean) envCtx.lookup("bean/MyBeanFactory");
writer.println("foo = " + bean.getFoo() + ", bar = " +
bean.getBar());
4. Configure Tomcat's Resource Factory
To configure Tomcat's resource factory, add an elements like this to the element for this web application.
<Context ...>
...
<Resource name="bean/MyBeanFactory" auth="Container"
type="com.mycompany.MyBean"
factory="com.mycompany.MyBeanFactory"
singleton="false"
bar="23"/>
...
</Context>
Resource Link:
Adding Custom Resource Factories
How to Configure JNDI DataSource in Tomcat 8 with Java Configuration:
For adding external resource in tomcat 8, you can follow this link: Adding external resources to class-path in Tomcat 8

The question was about embedded tomcat.

simple string value by JNDI in Java

How can i set simple string value in configuration of tomcat and then read in java application?
context.xml
<ResourceLink name="global/test" global="testing" type="java.lang.String" />
server.xml
<Enviroment name="testing" value="myUser" type="java.lang.String"/>
web.xml in application
<resource-env-ref>
<resource-env-ref-name>global/test</resource-env-ref-name>
<resource-env-ref-type>java.lang.String</resource-env-ref-type>
</resource-env-ref>
in my java application
public String getValue(){
return new JndiDataSourceLookup().getDataSource("global/test").toString();
}
When i Run tomcat, i see these errors...
org.springframework.jdbc.datasource.lookup.DataSourceLookupFailureException: Failed to look up JNDI DataSource with name 'global/test'; nested exception is javax.naming.NameNotFoundException: Name [global/test] is not bound in this Context. Unable to find [global].
javax.naming.NameNotFoundException: Name [global/test] is not bound in this Context. Unable to find [global].

In your web.xml use,
<env-entry>
<description>Sample env entry</description>
<env-entry-name>isConnected</env-entry-name>
<env-entry-type>java.lang.Boolean</env-entry-type><!--order matters -->
<env-entry-value>true</env-entry-value>
</env-entry>
In code,
try {
Context initCxt = new InitialContext();
Boolean isConn = (Boolean)initCxt.lookup("java:comp/env/isConnected");
System.out.println(isConn.toString());
// one could use relative names into the sub-context
Context envContext = (Context) initCxt.lookup("java:comp/env");
Boolean isConn2 = (Boolean)envContext.lookup("isConnected");
System.out.println(isConn2.toString());
} catch (NamingException e) {
e.printStackTrace();
}
Have a look here Naming service tutorial to get a good understanding of InitialContext and JNDI.

I don't know what's inside JndiDataSourceLookup().getDataSource("global/test") but by the name of it, it should return a DataSoruce not a string.
If your lookup is local, simply do
Context ctx = new InitialContext();
String s = (String) ctx.lookup("global/test");
or if you are in a javaee container,
#Resource(name="global/test")
String testString;
and finally in your ejb-jar.xml
<env-entry>
<description>The name was explicitly set in the annotation so the classname prefix isn't required</description>
<env-entry-name>global/test</env-entry-name>
<env-entry-type>java.lang.String</env-entry-type>
<env-entry-value>StringValue</env-entry-value>
</env-entry>
Refer this link: http://tomee.apache.org/examples-trunk/injection-of-env-entry/README.html
Your configuration of context.xml, server.xml, and web.xml aren't gonna work.

Pattern for JDNI datasource

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. E.g. questions are
Where should the DataSource be allocated by calling ctx.lookup()? On method level or class scope? E.g. 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)
How can I verify the execution of several options of the DataSource, e.g. 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).
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

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 !!

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.

Cannot find dataSource, even though the dataSource is defined in context.xml

I have the following bean declared for one particular dao method to use a different data source than the rest of the project.
#Bean(name="kingsDataSource")
public DataSource kingsDataSource(){
JndiDataSourceLookup jndi = new JndiDataSourceLookup();
jndi.setResourceRef(true);
return jndi.getDataSource("dataSource/kings");
Here's the use of that bean.
#Resource(name="kingsDataSource")
private DataSource ds;
Here's from the context.xml (omitting the user and password, which have been verified to be correct, and would have been throwing a different error if they were wrong anyway.) I have also played with putting this in the context.xml of the server, having it in one place and not the other, and having it in both places.
<Resource
name="dataSource/kings"
auth="Container"
type="com.mysql.jdbc.jdbc2.optional.MysqlDataSource"
factory="org.apache.naming.factory.BeanFactory"
URL="jdbc:mysql://kings/db_netlogs" />
The error is a name not found exception -
Caused by: javax.naming.NameNotFoundException: Name [dataSource/kings] is
not bound in this Context. Unable to find [dataSource].
My question, then, is - to what do I bind this and how?

try to add a resource-ref to your web.xml
<resource-ref>
<res-ref-name>dataSource/kings</res-ref-name>
<res-type>javax.sql.DataSource</res-type>
<res-auth>Container</res-auth>
<res-sharing-scope>Shareable</res-sharing-scope>
</resource-ref>

Accessing attributes of resource from context.xml in program

Is there a way in java to access the values of the resource tag given in the context.xml from the program?
<Context ...>
...
<Resource name="jdbc/EmployeeDB" auth="Container"
type="javax.sql.DataSource" username="dbusername" password="dbpassword"
driverClassName="org.hsql.jdbcDriver" url="jdbc:HypersonicSQL:database"
maxActive="8" maxIdle="4"/>
...
</Context>
I know that we can get the the datasource the following way:
Context initCtx = new InitialContext();
Context envCtx = (Context) initCtx.lookup("java:comp/env");
DataSource ds = (DataSource)
envCtx.lookup("jdbc/EmployeeDB");
Connection conn = ds.getConnection();
... use this connection to access the database ...
conn.close();
But is there a way to print the userName and password in the program that i give in the resource tag?

You can try to cast it to actual implementation of the resource (print out the name with .getClass().getName()) and use the methods provided there. For example tomcat's BasicDataSource has getPassword getUser methods.