The GlobalNamingResources Component

Table of Contents

Introduction

The GlobalNamingResources element defines the global JNDI resources for the Server.

These resources are listed in the server's global JNDI resource context. This context is distinct from the per-web-application JNDI contexts described in the JNDI Resources How-To. The resources defined in this element are not visible in the per-web-application contexts unless you explicitly link them with <ResourceLink> elements.

Attributes

Nested Components

Special Features

Environment Entries

You can configure named values that will be made visible to all web applications as environment entry resources by nesting <Environment> entries inside this element. For example, you can create an environment entry like this:

<GlobalNamingResources ...>
  ...
  <Environment name="maxExemptions" value="10"
         type="java.lang.Integer" override="false"/>
  ...
</GlobalNamingResources>

This is equivalent to the inclusion of the following element in the web application deployment descriptor (/WEB-INF/web.xml): 

<env-entry>
  <env-entry-name>maxExemptions</env-entry-name>
  <env-entry-value>10</env-entry-value>
  <env-entry-type>java.lang.Integer</env-entry-type>
</env-entry>

but does not require modification of the deployment descriptor to customize this value.

The valid attributes for an <Environment> element are as follows:

Attribute Description
description

Optional, human-readable description of this environment entry.

name

The name of the environment entry to be created, relative to the java:comp/env context.

override

Set this to false if you do not want an <env-entry> for the same environment entry name, found in the web application deployment descriptor, to override the value specified here. By default, overrides are allowed.

type

The fully qualified Java class name expected by the web application for this environment entry. Must be a legal value for <env-entry-type> in the web application deployment descriptor.

value

The parameter value that will be presented to the application when requested from the JNDI context. This value must be convertible to the Java type defined by the type attribute.

Resource Definitions

You can declare the characteristics of resources to be returned for JNDI lookups of <resource-ref> and <resource-env-ref> elements in the web application deployment descriptor by defining them in this element and then linking them with <ResourceLink> elements in the <Context> element. You MUST also define any other needed parameters using attributes on the Resource element, to configure the object factory to be used (if not known to Tomcat already), and the properties used to configure that object factory.

For example, you can create a resource definition like this:

<GlobalNamingResources ...>
  ...
  <Resource name="jdbc/EmployeeDB" auth="Container"
            type="javax.sql.DataSource"
     description="Employees Database for HR Applications"/>
  ...
</GlobalNamingResources>

This is equivalent to the inclusion of the following element in the web application deployment descriptor (/WEB-INF/web.xml):

<resource-ref>
  <description>Employees Database for HR Applications</description>
  <res-ref-name>jdbc/EmployeeDB</res-ref-name>
  <res-ref-type>javax.sql.DataSource</res-ref-type>
  <res-auth>Container</res-auth>
</resource-ref>

but does not require modification of the deployment descriptor to customize this value.

The valid attributes for a <Resource> element are as follows:

Attribute Description
auth

Specify whether the web Application code signs on to the corresponding resource manager programmatically, or whether the Container will sign on to the resource manager on behalf of the application. The value of this attribute must be Application or Container. This attribute is required if the web application will use a <resource-ref> element in the web application deployment descriptor, but is optional if the application uses a <resource-env-ref> instead.

closeMethod

Name of the zero-argument method to call on a singleton resource when it is no longer required. This is intended to speed up clean-up of resources that would otherwise happen as part of garbage collection. This attribute is ignored if the singleton attribute is false. If not specified, no default is defined and no close method will be called.

For Apache Commons DBCP 2 and Apache Tomcat JDBC connection pools you can use closeMethod="close". Note that Apache Commons DBCP 2 requires this to be set for a clean shutdown. When using the default Tomcat connection pool (based on DBCP 2) Tomcat will set this attribute automatically unless it is explicitly set to the empty string.

description

Optional, human-readable description of this resource.

name

The name of the resource to be created, relative to the java:comp/env context.

scope

Specify whether connections obtained through this resource manager can be shared. The value of this attribute must be Shareable or Unshareable. By default, connections are assumed to be shareable.

singleton

Specify whether this resource definition is for a singleton resource, i.e. one where there is only a single instance of the resource. If this attribute is true, multiple JNDI lookups for this resource will return the same object. If this attribute is false, multiple JNDI lookups for this resource will return different objects. This attribute must be true for javax.sql.DataSource resources to enable JMX registration of the DataSource. The value of this attribute must be true or false. By default, this attribute is true.

type

The fully qualified Java class name expected by the web application when it performs a lookup for this resource.

Use <ResourceLink> elements to link resources from the global context into per-web-application contexts. Here is an example of making a custom factory available to an application, based on the example definition in the JNDI Resource How-To: 

<Context>
  <ResourceLink
    name="bean/MyBeanFactory"
    global="bean/MyBeanFactory"
    type="com.mycompany.MyBean"
  />
</Context>

Transaction

You can declare the characteristics of the UserTransaction to be returned for JNDI lookup for java:comp/UserTransaction. You MUST define an object factory class to instantiate this object as well as the needed resource parameters as attributes of the Transaction element, and the properties used to configure that object factory.

The valid attributes for the <Transaction> element are as follows:

Attribute Description
factory

The class name for the JNDI object factory.