[[jmx-interface]]
= Controlling the Management Interface of Your Beans

In the example in the xref:integration/jmx/exporting.adoc#jmx-exporting-registration-behavior[preceding section],
you had little control over the management interface of your bean. All of the `public`
properties and methods of each exported bean were exposed as JMX attributes and
operations, respectively. To exercise finer-grained control over exactly which
properties and methods of your exported beans are actually exposed as JMX attributes
and operations, Spring JMX provides a comprehensive and extensible mechanism for
controlling the management interfaces of your beans.


[[jmx-interface-assembler]]
== Using the `MBeanInfoAssembler` API

Behind the scenes, the `MBeanExporter` delegates to an implementation of the
`org.springframework.jmx.export.assembler.MBeanInfoAssembler` API, which is
responsible for defining the management interface of each bean that is exposed.
The default implementation,
`org.springframework.jmx.export.assembler.SimpleReflectiveMBeanInfoAssembler`,
defines a management interface that exposes all public properties and methods
(as you saw in the examples in the preceding sections). Spring provides two
additional implementations of the `MBeanInfoAssembler` interface that let you
control the generated management interface by using either source-level metadata
or any arbitrary interface.


[[jmx-interface-metadata]]
== Using Source-level Metadata: Java Annotations

By using the `MetadataMBeanInfoAssembler`, you can define the management interfaces for
your beans by using source-level metadata. The reading of metadata is encapsulated by the
`org.springframework.jmx.export.metadata.JmxAttributeSource` interface. Spring JMX
provides a default implementation that uses Java annotations, namely
`org.springframework.jmx.export.annotation.AnnotationJmxAttributeSource`. You must
configure the `MetadataMBeanInfoAssembler` with an implementation instance of the
`JmxAttributeSource` interface for it to function correctly, since there is no default.

To mark a bean for export to JMX, you should annotate the bean class with the
`@ManagedResource` annotation. You must annotate each method you wish to expose as an
operation with the `@ManagedOperation` annotation and annotate each property you wish to
expose with the `@ManagedAttribute` annotation. When annotating properties, you can omit
either the annotation of the getter or the setter to create a write-only or read-only
attribute, respectively.

NOTE: A `@ManagedResource`-annotated bean must be public, as must the methods exposing
operations or attributes.

The following example shows an annotated version of the `JmxTestBean` class that we
used in xref:integration/jmx/exporting.adoc#jmx-exporting-mbeanserver[Creating an MBeanServer].

[source,java,indent=0,subs="verbatim,quotes",chomp="-packages"]
----
	package org.springframework.jmx;

	@ManagedResource(
			objectName="bean:name=testBean4",
			description="My Managed Bean",
			log=true,
			logFile="jmx.log",
			currencyTimeLimit=15,
			persistPolicy="OnUpdate",
			persistPeriod=200,
			persistLocation="foo",
			persistName="bar")
	public class AnnotationTestBean {

		private int age;
		private String name;

		public void setAge(int age) {
			this.age = age;
		}

		@ManagedAttribute(description="The Age Attribute", currencyTimeLimit=15)
		public int getAge() {
			return this.age;
		}

		@ManagedAttribute(description="The Name Attribute",
				currencyTimeLimit=20,
				defaultValue="bar",
				persistPolicy="OnUpdate")
		public void setName(String name) {
			this.name = name;
		}

		@ManagedAttribute(defaultValue="foo", persistPeriod=300)
		public String getName() {
			return this.name;
		}

		@ManagedOperation(description="Add two numbers")
		@ManagedOperationParameter(name = "x", description = "The first number")
		@ManagedOperationParameter(name = "y", description = "The second number")
		public int add(int x, int y) {
			return x + y;
		}

		public void dontExposeMe() {
			throw new RuntimeException();
		}

	}
----

In the preceding example, you can see that the `AnnotationTestBean` class is annotated
with `@ManagedResource` and that this `@ManagedResource` annotation is configured
with a set of attributes. These attributes can be used to configure various aspects
of the MBean that is generated by the `MBeanExporter` and are explained in greater
detail later in xref:integration/jmx/interface.adoc#jmx-interface-metadata-types[Spring JMX Annotations].

Both the `age` and `name` properties are annotated with `@ManagedAttribute`,
but, in the case of the `age` property, only the getter method is annotated.
This causes both of these properties to be included in the management interface
as managed attributes, but the `age` attribute is read-only.

Finally, the `add(int, int)` method is annotated with `@ManagedOperation`,
whereas the `dontExposeMe()` method is not. This causes the management interface to
contain only one operation (`add(int, int)`) when you use the `MetadataMBeanInfoAssembler`.

NOTE: The `AnnotationTestBean` class is not required to implement any Java interfaces,
since the JMX management interface is derived solely from annotations.

The following configuration shows how you can configure the `MBeanExporter` to use the
`MetadataMBeanInfoAssembler`:

[source,xml,indent=0,subs="verbatim,quotes"]
----
	<beans>

		<bean id="exporter" class="org.springframework.jmx.export.MBeanExporter">
			<property name="assembler" ref="assembler"/>
			<property name="namingStrategy" ref="namingStrategy"/>
			<property name="autodetect" value="true"/>
		</bean>

		<!-- will create management interface using annotation metadata -->
		<bean id="assembler"
				class="org.springframework.jmx.export.assembler.MetadataMBeanInfoAssembler">
			<property name="attributeSource" ref="jmxAttributeSource"/>
		</bean>

		<!-- will pick up the ObjectName from the annotation -->
		<bean id="namingStrategy"
				class="org.springframework.jmx.export.naming.MetadataNamingStrategy">
			<property name="attributeSource" ref="jmxAttributeSource"/>
		</bean>

		<bean id="jmxAttributeSource"
				class="org.springframework.jmx.export.annotation.AnnotationJmxAttributeSource"/>

		<bean id="testBean" class="org.springframework.jmx.AnnotationTestBean">
			<property name="name" value="TEST"/>
			<property name="age" value="100"/>
		</bean>

	</beans>
----

In the preceding example, a `MetadataMBeanInfoAssembler` bean has been configured with an
instance of the `AnnotationJmxAttributeSource` class and passed to the `MBeanExporter`
through the assembler property. This is all that is required to take advantage of
annotation-driven management interfaces for your Spring-exposed MBeans.


[[jmx-interface-metadata-types]]
== Spring JMX Annotations

The following table describes the annotations that are available for use in Spring JMX:

[[jmx-metadata-types]]
.Spring JMX annotations
[cols="1,1,3"]
|===
| Annotation | Applies to | Description

| `@ManagedResource`
| Classes
| Marks all instances of a `Class` as JMX managed resources.

| `@ManagedNotification`
| Classes
| Indicates a JMX notification emitted by a managed resource.

| `@ManagedAttribute`
| Methods (only getters and setters)
| Marks a getter or setter as one half of a JMX attribute.

| `@ManagedMetric`
| Methods (only getters)
| Marks a getter as a JMX attribute, with added descriptor properties to indicate that it is a metric.

| `@ManagedOperation`
| Methods
| Marks a method as a JMX operation.

| `@ManagedOperationParameter`
| Methods
| Defines a description for an operation parameter.
|===

The following table describes some of the common attributes that are available for use in
these annotations. Consult the Javadoc for each annotation for further details.

[[jmx-metadata-parameters]]
.Spring JMX annotation attributes
[cols="1,1,3"]
|===
| Attribute | Applies to | Description

| `objectName`
| `@ManagedResource`
| Used by `MetadataNamingStrategy` to determine the `ObjectName` of a managed resource.

| `description`
| `@ManagedResource`, `@ManagedNotification`, `@ManagedAttribute`, `@ManagedMetric`,
  `@ManagedOperation`, `@ManagedOperationParameter`
| Sets the description of the resource, notification, attribute, metric, or operation.

| `currencyTimeLimit`
| `@ManagedResource`, `@ManagedAttribute`, `@ManagedMetric`
| Sets the value of the `currencyTimeLimit` descriptor field.

| `defaultValue`
| `@ManagedAttribute`
| Sets the value of the `defaultValue` descriptor field.

| `log`
| `@ManagedResource`
| Sets the value of the `log` descriptor field.

| `logFile`
| `@ManagedResource`
| Sets the value of the `logFile` descriptor field.

| `persistPolicy`
| `@ManagedResource`, `@ManagedMetric`
| Sets the value of the `persistPolicy` descriptor field.

| `persistPeriod`
| `@ManagedResource`, `@ManagedMetric`
| Sets the value of the `persistPeriod` descriptor field.

| `persistLocation`
| `@ManagedResource`
| Sets the value of the `persistLocation` descriptor field.

| `persistName`
| `@ManagedResource`
| Sets the value of the `persistName` descriptor field.

| `name`
| `@ManagedOperationParameter`
| Sets the display name of an operation parameter.

| `index`
| `@ManagedOperationParameter`
| Sets the index of an operation parameter.
|===


[[jmx-interface-autodetect]]
== Using the `AutodetectCapableMBeanInfoAssembler` Interface

To simplify configuration even further, Spring includes the
`AutodetectCapableMBeanInfoAssembler` interface, which extends the `MBeanInfoAssembler`
interface to add support for auto-detection of MBean resources. If you configure the
`MBeanExporter` with an instance of `AutodetectCapableMBeanInfoAssembler`, it is
allowed to "vote" on the inclusion of beans for exposure to JMX.

The only implementation of the `AutodetectCapableMBeanInfo` interface is
the `MetadataMBeanInfoAssembler`, which votes to include any bean that is marked
with the `ManagedResource` attribute. The default approach in this case is to use the
bean name as the `ObjectName`, which results in configuration similar to the following:

[source,xml,indent=0,subs="verbatim,quotes"]
----
	<beans>

		<bean id="exporter" class="org.springframework.jmx.export.MBeanExporter">
			<!-- notice how no 'beans' are explicitly configured here -->
			<property name="autodetect" value="true"/>
			<property name="assembler" ref="assembler"/>
		</bean>

		<bean id="assembler" class="org.springframework.jmx.export.assembler.MetadataMBeanInfoAssembler">
			<property name="attributeSource">
				<bean class="org.springframework.jmx.export.annotation.AnnotationJmxAttributeSource"/>
			</property>
		</bean>

		<bean id="testBean" class="org.springframework.jmx.AnnotationTestBean">
			<property name="name" value="TEST"/>
			<property name="age" value="100"/>
		</bean>

	</beans>
----

Notice that, in the preceding configuration, no beans are passed to the `MBeanExporter`.
However, the `AnnotationTestBean` is still registered, since it is annotated with
`@ManagedResource` and the `MetadataMBeanInfoAssembler` detects this and votes to include
it. The only downside with this approach is that the name of the `AnnotationTestBean` now
has business meaning. You can address this issue by configuring an `ObjectNamingStrategy`
as explained in xref:integration/jmx/naming.adoc[Controlling `ObjectName` Instances for
Your Beans]. You can also see an example which uses the `MetadataNamingStrategy` in
xref:integration/jmx/interface.adoc#jmx-interface-metadata[Using Source-level Metadata: Java Annotations].



[[jmx-interface-java]]
== Defining Management Interfaces by Using Java Interfaces

In addition to the `MetadataMBeanInfoAssembler`, Spring also includes the
`InterfaceBasedMBeanInfoAssembler`, which lets you constrain the methods and
properties that are exposed based on the set of methods defined in a collection of
interfaces.

Although the standard mechanism for exposing MBeans is to use interfaces and a simple
naming scheme, `InterfaceBasedMBeanInfoAssembler` extends this functionality by
removing the need for naming conventions, letting you use more than one interface
and removing the need for your beans to implement the MBean interfaces.

Consider the following interface, which is used to define a management interface for the
`JmxTestBean` class that we showed earlier:

[source,java,indent=0,subs="verbatim,quotes"]
----
	public interface IJmxTestBean {

		public int add(int x, int y);

		public long myOperation();

		public int getAge();

		public void setAge(int age);

		public void setName(String name);

		public String getName();

	}
----

This interface defines the methods and properties that are exposed as operations and
attributes on the JMX MBean. The following code shows how to configure Spring JMX to use
this interface as the definition for the management interface:

[source,xml,indent=0,subs="verbatim,quotes"]
----
	<beans>

		<bean id="exporter" class="org.springframework.jmx.export.MBeanExporter">
			<property name="beans">
				<map>
					<entry key="bean:name=testBean5" value-ref="testBean"/>
				</map>
			</property>
			<property name="assembler">
				<bean class="org.springframework.jmx.export.assembler.InterfaceBasedMBeanInfoAssembler">
					<property name="managedInterfaces">
						<value>org.springframework.jmx.IJmxTestBean</value>
					</property>
				</bean>
			</property>
		</bean>

		<bean id="testBean" class="org.springframework.jmx.JmxTestBean">
			<property name="name" value="TEST"/>
			<property name="age" value="100"/>
		</bean>

	</beans>
----

In the preceding example, the `InterfaceBasedMBeanInfoAssembler` is configured to use the
`IJmxTestBean` interface when constructing the management interface for any bean. It is
important to understand that beans processed by the `InterfaceBasedMBeanInfoAssembler`
are not required to implement the interface used to generate the JMX management
interface.

In the preceding case, the `IJmxTestBean` interface is used to construct all management
interfaces for all beans. In many cases, this is not the desired behavior, and you may
want to use different interfaces for different beans. In this case, you can pass
`InterfaceBasedMBeanInfoAssembler` a `Properties` instance through the `interfaceMappings`
property, where the key of each entry is the bean name and the value of each entry is a
comma-separated list of interface names to use for that bean.

If no management interface is specified through either the `managedInterfaces` or
`interfaceMappings` properties, the `InterfaceBasedMBeanInfoAssembler` reflects
on the bean and uses all of the interfaces implemented by that bean to create the
management interface.


[[jmx-interface-methodnames]]
== Using `MethodNameBasedMBeanInfoAssembler`

`MethodNameBasedMBeanInfoAssembler` lets you specify a list of method names
that are exposed to JMX as attributes and operations. The following code shows a sample
configuration:

[source,xml,indent=0,subs="verbatim,quotes"]
----
	<bean id="exporter" class="org.springframework.jmx.export.MBeanExporter">
		<property name="beans">
			<map>
				<entry key="bean:name=testBean5" value-ref="testBean"/>
			</map>
		</property>
		<property name="assembler">
			<bean class="org.springframework.jmx.export.assembler.MethodNameBasedMBeanInfoAssembler">
				<property name="managedMethods">
					<value>add,myOperation,getName,setName,getAge</value>
				</property>
			</bean>
		</property>
	</bean>
----

In the preceding example, you can see that the `add` and `myOperation` methods are exposed as JMX
operations, and `getName()`, `setName(String)`, and `getAge()` are exposed as the
appropriate half of a JMX attribute. In the preceding code, the method mappings apply to
beans that are exposed to JMX. To control method exposure on a bean-by-bean basis, you can use
the `methodMappings` property of `MethodNameMBeanInfoAssembler` to map bean names to
lists of method names.
