Month: February 2020

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Mulesoft 4: Using Java in Dataweave 2.0

Mule 4 introduces DataWeave 2.0 as the default expression language replacing Mule Expression Language (MEL). DataWeave 2.0 is tightly integrated with the Mule 4 runtime engine, which runs the scripts and expressions in your Mule application.

Since Dataweave 2.0 is default expression language for Mule 4, Dataweave can use almost all place within your Mule application. So, In some use-case Dataweave needs to call java method or instantiate java class to execute java complex business logic.

In my previous blog I explained usage of java within Mulesoft flow. In this blog I am explaining usage of java within Dataweave 2.0.

There are 2 ways we can use java within Dataweave code

  1. Calling java method
  2. Instantiate Java class
1. Calling java method — There is restriction with Dataweave when calling to java. you can only call Static methods via DataWeave (methods that belong to a Java class, not methods that belong to a specific instance of a class). Before making a method call from java class, you must import the class.

Here is Dataweave code

In dataweave this method can use multiple way

Import only method instead of the whole class:

%dw 2.0
import java!com::vanrish::AppUtils:: encode
output application/json
---
{
   encode:encode("mystring" as String)
}

import and call it in a single line:

%dw 2.0
output application/json
---
{ 
    encode: java!com::vanrish::AppUtils:: encode ("mystring" as String)
 }
2. Instantiate Java class – Dataweave allows to instantiate a new object of any java class but you can’t call its instance method through dataweave. You can refer it as variables.

%dw 2.0
import java!com::vanrish::AppUtils 
output application/json
---
{
     value: AppUtils::new().data
 }

AppUtils.java

package com.vanrish;

import sun.misc.BASE64Encoder;
/**
 * @author rajnish
 */
public class AppUtils{
	public static final BASE64Encoder encoder = new BASE64Encoder();
        private String data;
	
	/**
	 * @param plainString
	 * @return
	 */
	public static String encode(String plainString)
	{
		String encodedString = encoder.encodeBuffer(plainString.getBytes());
		return encodedString;
	}

/**
	 * @param dataStr
	 * @return
	 */
	public String getData(String dataStr)
	{
              data = dataStr+" : test";
              return  data;
	}
}

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MuleSoft 4: Using Java in Mule Flow

MuleSoft is a lightweight integration and API platform that allows you to connect anything anywhere and enable your data through API. Mule evolved from java and spring framework. MuleSoft supports multiple language although all Mule module are developed in java.

 Since Mule evolved from java it has capability to use direct java class and method in Mule flow. This capability gives flexibility to Mule developer to use java for complex business logic.

There are several ways you can use java within Mule. Here are some of Java modules available to use within MuleSoft application

There are 4 java modules are available in MuleSoft flow

  1. New
  2. Invoke
  3. Invoke static
  4. Validate type

To explain all these components and uses in Mule flow I created Utils.java and AppUtils.java classes

1. New – AppUtils.java class instantiation can be achieved by calling constructor of this class through MuleSoft New component within Mule flow.

AppUtils java class defined 2 contractors, So Mule constructor properties for NEW component is showing 2 options.

New module without parameter

<java:new doc:name="Instantiate appUtils" doc:id="22ddcb7e-82ed-40f8-bc11-b779ceedd1a1"
    constructor="AppUtils()"  class="com.vanrish.AppUtils" target="appInst">
</java:new>

New module with parameter

<java:new doc:name="Instantiate appUtils" doc:id="22ddcb7e-82ed-40f8-bc11-b779ceedd1a1"
    constructor="AppUtils(String)"  class="com.vanrish.AppUtils" target="appInst">
    <java:args ><![CDATA[#[{paramVal:"Hello world}]]]>
</java:new>

In above code, Instance of AppUtils class is created and placed into the “appInst”  target variables to reuse same instance in Mule flow.

New module
2. Invoke – In new java module we instantiate AppUtils.java class and placed into “appInst” variable. Now to use this variable set Invoke module and call one of method define in AppUtils.java class. In AppUtils.java class, there is one non static method “generateRandomNumber” defined with String parameter. In example we call this method through Invoke module. 
<java:invoke doc:name="Invoke" doc:id="9348e2cf-87fe-4ff7-958c-f430d0421702"
      instance="#[vars.appInst]" class="com.vanrish.AppUtils" method="generateRandomNumber(String)">
     <java:args ><![CDATA[#[{numVal:”100”}]]]></java:args>
</java:invoke>
Invoke module
3. Invoke static—Invoke static java module enable mule flow to call java static method. This is one of the easy ways to call any java method in Mule flow.

Mule code is calling to java static method

<java:invoke-static doc:name="Invoke static" doc:id="bc3e110c-d970-47ef-891e-93fb3ffb61bd" 
  class="com.vanrish.AppUtils" method="encode(String)">
   <java:args ><![CDATA[#[{plainString:"mystringval"}]]]></java:args>
</java:invoke-static>
Invoke-static module
4. Validate type – Validate type java module use instance of method from java. This module accepts “Accept subtypes” parameter which indicates if the operation should accept all subclasses of a class. By default it acceptSubtypes=“true” which means it will accept all sub class of main class but if it will set as false acceptSubtypes=“false” then during execution the operation throws an error (JAVA:WRONG_INSTANCE_CLASS) 
<java:validate-type doc:name="Validate type" doc:id="288c791c-50eb-4be0-b924-56481dfdc023"
 class="com.vanrish.Utils" instance="#[vars.appInst]" acceptSubtypes="false"/>
Validate-type module

Java in Mule flow diagram

java in Mule flow

Utils.java

package com.vanrish;

public class Utils{
	
}

AppUtils.java

package com.vanrish;
import java.util.Random;
import sun.misc.BASE64Encoder;
/**
 * @author rajnish
 */
public class AppUtils extends Utils {
	public static final BASE64Encoder encoder = new BASE64Encoder();
	//Constructor without Parameter
	public AppUtils(){
		System.out.println("Constructor with no parameter");
	}
	//Constructor with Parameter
  public AppUtils(String paramVal){
		System.out.println("Constructor with parameter value="+paramVal);
	}
	/**
	 * @param String
	 * @return
	 */
	public  String generateRandomNumber(String numVal) {
		Integer numNoRange = null;
		  Random rand = new Random();
		  if(numVal !=null) {
			  numNoRange = rand.nextInt(new Integer(numVal));
		  }else {
		   numNoRange = rand.nextInt();
		  }
	    return numNoRange.toString();
	}
	/**
	 * @param plainString
	 * @return
	 */
	public static String encode(String plainString)
	{
		String encodedString = encoder.encodeBuffer(plainString.getBytes());
		return encodedString;
	}
}

Mulesoft Code

<?xml version="1.0" encoding="UTF-8"?>
<mule xmlns:java="http://www.mulesoft.org/schema/mule/java" xmlns:db="http://www.mulesoft.org/schema/mule/db"
xmlns:ee="http://www.mulesoft.org/schema/mule/ee/core" 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:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="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
http://www.mulesoft.org/schema/mule/ee/core http://www.mulesoft.org/schema/mule/ee/core/current/mule-ee.xsd
http://www.mulesoft.org/schema/mule/hl7 http://www.mulesoft.org/schema/mule/hl7/current/mule-hl7.xsd
http://www.mulesoft.org/schema/mule/db
 http://www.mulesoft.org/schema/mule/db/current/mule-db.xsdhttp://www.mulesoft.org/schema/mule/java http://www.mulesoft.org/schema/mule/java/current/mule-java.xsd">

<http:listener-config name="HTTP_Listener_config" doc:name="HTTP Listener config" doc:id="af3ce281-bf68-4c7b-83fb-52b2d2506677" >

<http:listener-connection host="0.0.0.0" port="8081" />
</http:listener-config>
<flow name="helloworldFlow" doc:id="a13826dc-67a1-4cda-8133-bc16a59ddba2" >
  <http:listener doc:name="Listener" doc:id="82522c77-5c33-4003-820a-7a04b51c3001" config-ref="HTTP_Listener_config" path="helloworld"/>
  <logger level="INFO" doc:name="Logger" doc:id="b40bc107-1ab5-4a3f-8f20-d7dfb63e5acb" message="entering flow"/>
  <java:new doc:name="Instantiate appUtils" doc:id="c1854580-f4d4-4e5c-a34d-7ca185152d02"
constructor="AppUtils(String)" class="com.vanrish.AppUtils" target="appInst" 
 >
  <java:args ><! 
  [CDATA[#[{
      paramVal:"Hello world"
  }]]]></java:args>
  </java:new>

 <java:invoke doc:name="Invoke" doc:id="9348e2cf-87fe-4ff7-958c-f430d0421702" instance="#[vars.appInst]" class="com.vanrish.AppUtils" method="generateRandomNumber(String)">
<java:args ><![CDATA[#[{
numVal:null
}]]]></java:args>
</java:invoke>
<java:invoke-static doc:name="Invoke static" doc:id="bc3e110c-d970-47ef-891e-93fb3ffb61bd" class="com.vanrish.AppUtils" method="encode(String)">
<java:args ><![CDATA[#[{
  plainString:"mystringval"
}]]]></java:args>
</java:invoke-static>
<java:validate-type doc:name="Validate type" doc:id="288c791c-50eb-4be0-b924-56481dfdc023" class="com.vanrish.Utils" instance="#[vars.appInst]"/>
<set-payload value="Success" doc:name="Set Payload" doc:id="8b6c9c0b-07c8-4e17-b649-2c24d4da8bea" />
</flow>
</mule>