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  5. Invoke Component Reference

Invoke Component Reference

The Invoke component invokes a method of an object defined in a Spring bean. You can provide an array of argument expressions to map the message to the method arguments. Mule determines which method to use via the method name, along with the number of argument expressions provided. Mule automatically transforms the results of the argument expressions to match the method argument type, where possible.

Note: Mule does not support multiple methods with the same name and same number of arguments.

Configuring the Java Class

Use the Invoke component when you have an existing method defined in custom Java code that you wish to use in processing a message:

  1. Create a new Mule project. Click File > New > Mule Project and name the project demo.

  2. Create a new Java class. In Package Explorer, right-click src/main/java and click New > Class.

    invoke create class

  3. Name the class GreetingService.

    Create a Java Class

    The GreetingService.java file opens in Studio.

  4. For this example, ensure that your completed class has this code:

    package demo;
public class GreetingService {
    public String sayHello(String name) {
        return String.format("Hello %s!", name);
    }
    public String sayGoodbye(String name) {
        return String.format("Goodbye %s!", name);
    }
}

    The package is the name of your application. The GreetingService class contains two methods:

    • sayHello - Displays "Hello <name>"

    • sayGoodbye - Displays "Goodbye <name>"

Configure Your Application

Studio Visual Editor

  1. In Studio, search for "http" and place an HTTP Connector on the canvas.

    invoke http icon

  2. Click the HTTP Connector to display its properties menu. Click the green plus sign to the right of Connector Configuration.

    invoke http pe

    In the Global Element Properties window, set the host to localhost and the port to 8081. Leave all other settings the same and click OK.

    HTTP Global Element Properties

  3. In the HTTP Connector’s property editor, set Path to /greeting:

    invoke http path

  4. Search for "invoke" and drag the Invoke Component to the canvas:

    invoke flow

  5. Click the Invoke icon to open the property editor:

    invoke pe blank

    The possible values in the property editor are:

    Attribute Description

    Display Name

    Customize to display a unique name for the component in your application. Not required for Mule Standalone. The default is Invoke.

    Name

    The name of the message processor for logging purposes, for example, someName.

    Object Ref

    (Required) Reference to the object containing the method to be invoked. In the example, use GreetingService.

    Method

    (Required) The name of the method to be invoked. In the example, use sayHello.

    Method Arguments

    Comma-separated list of Mule expressions that, when evaluated, provide the arguments for the method invocation. For example, [1], #[2]. In the example, we use [message.inboundProperties.'http.query.params'.name]

    Method Argument Types

    Comma-separated list of argument types for the method invocation. Use when you have more than one method with the same name in your class. For example, java.lang.Float, java.lang.String

  6. Set Object Ref to the object containing the method to be invoked, in this case, GreetingService.

  7. Set Method to the method to invoke, in this case, sayHello.

  8. Set Method Arguments to #[message.inboundProperties.'http.query.params'.name].

    Invoke Property Editor with Values

XML Editor or Standalone

Include the invoke method in your flow, and define a Spring bean as a global element with the reference to the object containing the method.

<spring:beans>
  <spring:bean name="beanName" class="invoke.GreetingService"/>
</spring:beans>

<flow
  ...
      <invoke object-ref="GreetingService" method="sayHello" methodArguments="#[1], #[2]" methodArgumentTypes="java.lang.Float, java.lang.Float" name="someName" doc:name="Invoke"/>
  ...
</flow>
Element Description

invoke

Invokes a method in a specified object using method arguments determined by Mule expressions.

Attributes:

Field Description Example XML

doc:name

Customize to display a unique name for the component in your application.

doc:name="Invoke"

name

The name of the message processor for logging purposes.

name="someName"

object-ref

(Required) Reference to the class or object containing the method to be invoked.

object-ref="GreetingService"`

method

(Required) The name of the method to be invoked.

method="sayHello"

methodArguments

Comma-separated list of Mule expressions that, when evaluated, are the arguments for the method invocation.

methodArguments="#[1], #[2]"

methodArgumentTypes

Comma-separated list of argument types for the method invocation. Use when you have more than one method with the same name in your class.

`methodArgumentTypes="java.lang.Float, java.lang.Float" `

Create Your Spring Bean

To reference your Java, Mule requires a Spring bean to declare the class path.

Studio Visual Editor

  1. In Anypoint Studio, click Global Element at the bottom of the Canvas.

  2. In the Global Mule Configuration Elements screen, click Create.

    invoke create bean

  3. In the Choose Global Type screen, expand Beans, select Bean, and click OK.

    invoke select bean

  4. In the Global Element Properties menu, enter the class name.

XML Editor or Standalone

Add this Spring bean to your code after the <mule element:

<spring:beans>
    <spring:bean name="greetingService" class="invoke.GreetingService"/>
</spring:beans>

The complete source is:

<?xml version="1.0" encoding="UTF-8"?>

<mule xmlns:http="http://www.mulesoft.org/schema/mule/http" xmlns="http://www.mulesoft.org/schema/mule/core" xmlns:doc="http://www.mulesoft.org/schema/mule/documentation"
	xmlns:spring="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-current.xsd
http://www.mulesoft.org/schema/mule/core http://www.mulesoft.org/schema/mule/core/current/mule.xsd
http://www.mulesoft.org/schema/mule/http http://www.mulesoft.org/schema/mule/http/current/mule-http.xsd">
	<spring:beans>
	    <spring:bean name="greetingService" class="org.mule.invoke.GreetingService"/>
	</spring:beans>
    <http:listener-config name="HTTP_Listener_Configuration" host="localhost" port="8081" doc:name="HTTP Listener Configuration"/>
    <flow name="demoFlow">
        <http:listener config-ref="HTTP_Listener_Configuration" path="/greeting" doc:name="HTTP"/>
        <invoke object-ref="GreetingService" method="sayHello" doc:name="Invoke"/>
    </flow>
</mule>

Run and Test Your Project

To run and test your project from within Anypoint Studio:

  1. Click Run > Run As > Mule Application.

  2. Browse to http://localhost:8081/greeting?name=Mule which returns "Hello, Mule!" - You can change the name at the end of the URL in your browser to greet other people. You can also change the method in your setup to be sayGoodbye and the program then says goodbye to the name you specify.

  3. The browser appears like this:

See Also