7.9. Custom ClassLoader

In the Microcontainer you can define a custom ClassLoader per bean. When defining a classloader for the whole deployment, make sure you do not create a cyclic dependency -- for instance, a newly defined classloader that depends on itself.

Example 7.18. Defining a ClassLoader Per Bean

<classloader><inject bean="custom-classloader:0.0.0"/></classloader>
<!-- this will be explained in future article -->
<classloader name="custom-classloader" xmlns="urn:jboss:classloader:1.0" export-all="NON_EMPTY" import-all="true"/>
<bean name="CustomCL" class="org.jboss.demos.ioc.classloader.CustomClassLoader">
  <constructor>
    <parameter><inject bean="custom-classloader:0.0.0"/></parameter>
  </constructor>
  <property name="pattern">org\.jboss\.demos\.ioc\..+</property>
</bean>
<bean name="CB1" class="org.jboss.demos.ioc.classloader.CustomBean"/>
<bean name="CB2" class="org.jboss.demos.ioc.classloader.CustomBean">
  <classloader><inject bean="CustomCL"/></classloader>
</bean>
Example 7.19, “Custom ClassLoader Test” shows a test to verify that the CB2 bean uses a custom ClassLoader, which limits the loadable package scope.

Example 7.19. Custom ClassLoader Test

public class CustomClassLoader extends ClassLoader {
    private Pattern pattern;
    public CustomClassLoader(ClassLoader parent) {
	super(parent);
    }
    public Class<?> loadClass(String name) throws ClassNotFoundException {
	if (pattern == null || pattern.matcher(name).matches())
	    return super.loadClass(name);
	else
	    throw new ClassNotFoundException("Name '" + name + "' does not match pattern: " + pattern);
    }
    public void setPattern(String regexp) {
	pattern = Pattern.compile(regexp);
    }
}