Using the Java API

Introduction

This tutorial contains some examples of how to use the Java API provided by the Mendix Runtime. The tutorial assumes that you have some basic Java and Mendix modeling knowledge.

To avoid cluttering the tutorial, only the relevant code is shown, not the entire code generated by Studio Pro itself. Recreating the cases yourself and then trying to execute the actions is recommended.

When you look at these examples, often an IContext is used. This is the context in which something can be done. For example, it holds access rights to objects. If you do something with an object that requires access rights, the context in which you are working will determine whether you have these rights and can perform that action.

This how-to teaches you how to do the following:

• Execute microflows and commit objects
• Copy FileDocuments

Executing Microflows and Committing Objects

Sometimes you want to execute a microflow in a Java Action. This section explains how to do this, including how to pass parameters and obtain the return value. Additionally, the result will be saved in an object and the object will be committed.

In this example, you will execute a microflow that is called FormatString and is part of the MyFirstModule module. It has an input parameter called inputString, which is a string. Its return value is also a string, which contains the formatted string.

You can invoke the microflow directly using its proxy:

myfirstmodule.proxies.microflows.Microflows.formatString(getContext(), "this is an unformatted string");

But you can make your code more readable by first importing the proxy before the class declaration, and then referring to the microflow directly.

import static myfirstmodule.proxies.microflows.Microflows.formatString;
…
public class …
…
String formattedString = formatString(getContext(), "this is an unformatted string");
…

Once you have the value of the formatted string, you can store this in an object and then commit the object.

The code below formats the string "this is an unformatted string" using the microflow MyFirstModule.FormatString, stores it in the TestString attribute of an object of entity testObject, and then commits the object. The code is placed between BEGIN USER CODE and END USER CODE of the Java action.

import static myfirstmodule.proxies.microflows.Microflows.formatString;
…
public class …
…
// BEGIN USER CODE
String formattedString = formatString(getContext(), "this is an unformatted string");
testObject.setTestString(context, formattedString);
Core.commit(context, testObject.getMendixObject());
// END USER CODE
…

Copying FileDocuments

A FileDocument is a system module entity that holds the content of a file (for example, a text file or an Excel sheet). For this case, you have an entity called GenericObject that has a relation with an Attachment entity. The Attachment entity inherits from FileDocument. One GenericObject can have multiple Attachments. You copy the Attachments from one GenericObject to another so that they can be independently modified later.

In the Java Action, you pass two GenericObjects as parameters, a sourceObject and a destinationObject. You will also copy all the Attachments from the sourceObject to the destinationObject.

To be able to copy Attachments, you first need to retrieve them. For this purpose, we introduce the extra method called getAttachments, which returns a list of IMendixObjects. This code is put between BEGIN EXTRA CODE and END EXTRA CODE in the Java action.

public static List<IMendixObject> getAttachments(GenericObject object, IContext context) throws CoreException
{
	String attachmentEntityName = Attachment.entityName;
	String relationName = Attachment.MemberNames.Attachment_GenericObject.toString();
	String currentObjectID = object.getGUID();
	String query = String.format("//%s[%s=$currentid]", attachmentEntityName, relationName);
	return Core.createXPathQuery(query)
		.setVariable("currentid", currentObjectID)
		.execute(context);
}

Using the createXPathQuery API, you can also enter conditions, such as a sorting mechanism and a maximum number of objects returned. After executing the query, these are taken into account. View the JavaDoc for more information.

Now that you have a way to get all the Attachments from a certain GenericObject, you can start copying them.

This is the code between BEGIN USER CODE and END USER CODE:

Attachment newAttachment;
InputStream inputStream;
for (IMendixObject iMendixObject: getAttachments(sourceObject, context))
{
	inputStream = Core.getFileDocumentContent(iMendixObject);
	newAttachment = Attachment.create(context);
	newAttachment.setAttachment_GenericObject(destinationObject);
	Core.storeFileDocumentContent(context, newAttachment.getMendixObject(), (String) iMendixObject.getValue(system.proxies.Document.MemberNames.Name.toString()), inputStream);
}

After this, all Attachments belonging to one GenericObject are copied to another.

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