Invoke static custom Java methods in Mule 4

This example demonstrates how to use Mule 4's Java method to invoke a custom static method with 2 arguments. The custom class is reused from this post: Define and consume custom Java methods using Dataweave 2.0 in Mule 4.

Tips when working with custom java classes in Mule 4:

1. Include your custom namespace in mule-artifact.json
2. If you are making references to third party libraries, include them as maven dependencies in pom.xml

This is a simple example using a HTTP Listener to listen for POST requests to http://localhost:8081/list-files2

It takes in a parameter named path which could be a path to local folder, or a network folder.

After dragging the HTTP Listener from the design palette, drag a Java Invoke static component by typing Java in the search bar.

To configure the Java Invoke static method, take note that the arguments need to be passed in, Dataweave-style by enclosing them within #[].

If you are passing in more than 1 argument, enclose them within a map {}.

The argument format will be arg0:xxx, arg1:xxx and so on. Attempting to name the arguments otherwise results in errors during runtime.

I am going to invoke a static method called listOldFiles from my previous example.

public static ArrayList listOldFiles(String dir, Integer daysToRemainFiles) {}.

In the example below, I hardcoded 10 as the second argument to demonstrate how to assign values directly. This method will display files older than 10 days in the path specified from the client.

Finally, I include a Dataweave component to return the results in json as below:

Test request in POSTMAN:

Results:

Flow XML example:

      <flow name="invokeListFilesJavaFlow" doc:id="55ad8daf-b880-4a24-995b-0279f7ad1d6e" >  
           <http:listener doc:name="Listener" doc:id="62ca0aec-4d0c-44c2-8d98-1c4a28a3ba55" config-ref="HTTP_Listener_config" path="list-files2" allowedMethods="POST"/>  
           <java:invoke-static doc:name="Retrieve file list" doc:id="5e6f24c9-3921-405e-8af6-6f2adda8d607" class="customUtils.CustomFileUtil" method="listOldFiles(String,Integer)">  
                <java:args ><![CDATA[#[{ arg0:payload.path as String, arg1: 10 as Number }]]]></java:args>  
           </java:invoke-static>  
           <ee:transform doc:name="Transform Message" doc:id="26b5503b-6a1b-48d5-9411-de499f626ee6" >  
                <ee:message >  
                     <ee:set-payload ><![CDATA[%dw 2.0  
 output application/json  
 ---  
 {  
      results: payload  
 }]]></ee:set-payload>  
                </ee:message>  
           </ee:transform>  
      </flow>