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freemarker

Freemarker - How to get unprocessed content of custom directive?

I need to create a Freemarker directive that will pass the unprocessed content of the tag to a java method. The purpose is to load default template fragments into a DB so they can be examined and edited through another process, then output the result of the edited content if any. I have created a macro that almost does this, the problem is that the template fragment is processed before being passed to the java method.

Here is my current code:

<#macro process name>
    <#local content><#nested/></#local>
    ${myjava.processContent(name, content)}
</#macro>

<@process 'this-content-name'><p>This is some content about ${companyName}</p></@process>

Java:

//Add and instance of this class to the Freemarker data model for use in templates.
public class MyJava {

    public String processContent(String name, String content) {
        log.debug("Data To Process: name = {}, content = {}", name, content);

        String contentToOutput = getFromDb(name);
        if(contentToOutput == null) {
            insertContentInDb(name, content);
            contentToOutput = content;
        }
        
        TemplateModel model = Environment.getCurrentEnvironment().getDataModel();
        Configuration config = Environment.getCurrentEnvironment().getConfiguration();
        Template template = new Template("template-from-content", contentToOutput, config);
        return FreeMarkerTemplateUtils.processTemplateIntoString(template, model);
    }
}

When running the above I need to see the following logged:

Data To Process: name = this-content-name, content = <p>This is some content about ${companyName}</p>

Unfortunately I see this:

Data To Process: name = this-content-name, content = <p>This is some content about My Company Name</p>

The problem is clearly that the <#nested/> tag is processed by the template engine before it is stored in the local variable in my macro.

Looking into the Freemarker source code I see that Environment has invokeNestedContent() that appears to handle processing the content of the macro and appears to have methods for retrieving the raw content of the tag, i.e. <p>This is some content about ${companyName}</p>. Unfortunately those methods have package-private access and are not accessible from my code.

Is there another way to retrieve the RAW unprocessed content of a custom directive in Freemarker?

It seems like this would be very useful functionality for building content management systems.

Solution

  • Based on the suggestion in @ddekany's answer I was able to come up with two potential solutions which each have some trade offs.

    1. Using TemplateDirectiveModel and Environment.getCurrentDirectiveCallPlace() instead of a macro. The downside of this method is that I am not able to access the containing page's data_model when rendering the TemplateDirectiveModel. Additionally, the content retreived includes the full tag, not just its nested content so I have to parse that out.

    2. Implementing a freemarker utility class in package freemarker.core inside my own source tree. This allows me to access package-private methods, but is obviously not supported by Freemarker.

    Option 1 Java:

    @Slf4j
public class ContentTemplateDirective implements TemplateDirectiveModel {

    private HostData hostDataService;

    public ContentTemplateDirective(HostData hostDataService) {
        this.hostDataService = hostDataService;
    }

    @Override
    public void execute(Environment environment, Map params, TemplateModel[] loopVars,
                        TemplateDirectiveBody templateDirectiveBody) throws TemplateException, IOException {


        if (!params.containsKey("name")) {
            throw new TemplateModelException(
                    "This directive requires a 'name' parameter.");
        }
        if (loopVars.length != 0) {
            throw new TemplateModelException(
                    "This directive doesn't allow loop variables.");
        }

        String name = params.get("name").toString();
        log.debug("name = {}", name);

        String content = getRawDirectiveContent(true);
        content = hostDataService.removeTag(content, "<@content>");
        log.debug("content = {}", content);

        //This looks for an Element with this name in the DB. If it is not found it creates one with this content.
        //If it is found it overrides this content with the content from the DB.
        content = hostDataService.processElement(name, content, true);


        Configuration config = environment.getConfiguration();
        TemplateModel model = environment.getDataModel();
        Template template = new Template("string-template", content, config);

        StringWriter result = new StringWriter(1024);
        template.process(model, result);
        String output = result.toString();
        
        //Write the output.
        environment.getOut().write(output);
    }

    public static String getRawDirectiveContent(boolean trim) {
        log.debug("Getting Raw Directive Content");
        DirectiveCallPlace dcp = Environment.getCurrentEnvironment().getCurrentDirectiveCallPlace();

        String content =  dcp.getTemplate().getSource(dcp.getBeginColumn(), dcp.getBeginLine(), dcp.getEndColumn(), dcp.getEndLine());
        
        return trim ? content.trim() : content;
    }
}

    Option 1 FTL:

    <#assign content = "com.myapp.ContentTemplateDirective"?new(hostDataService)>

<!-- Does not work. Fails to find testValue when evaluating the content. -->
<#assign testValue>Some Test Value</#assign> 
<@content name='page.h2'><h2>This is the default content. Here is a test value: ${testValue}</h2></@content>

<!-- Works, but the testValue has to be assigned inside the <@content> tag so can't access externally assigned model attributes. -->
<@content name='page.h2'>
<#assign testValue>Some Test Value</#assign> 
<h2>This is the default content. Here is a test value: ${testValue}</h2></@content>

    Option 2 Java (in package freemarker.core):

    public class MyFreemarkerUtil {

    public static String getRawMacroContent(boolean trim) {
        log.debug("Getting Raw Macro Content");

        StringBuilder sb = new StringBuilder();

        Environment environment = Environment.getCurrentEnvironment();
        Macro.Context invokingMacroContext = environment.getCurrentMacroContext();
        TemplateObject callPlace = invokingMacroContext.callPlace;
        TemplateElement[] nestedContentBuffer = callPlace instanceof TemplateElement ? ((TemplateElement) callPlace).getChildBuffer() : null;
        if (nestedContentBuffer != null) {
            for (TemplateElement templateElement : nestedContentBuffer) {
                log.debug("templateElement = {}", templateElement);
                sb.append(templateElement.getSource());
            }
        }

        if(trim) {
            return sb.toString().trim();
        } else {
            return sb.toString();
        }
    }
}

    Option 2 FTL:

    <#macro content name>
    <#local temlateSource = hostDataService.processContent(name)/>
    <#local inlineTemplate = temlateSource?interpret/>
    <@inlineTemplate/>
</#macro>

<!-- This works. It is able to find the 'testValue' assigned outside the <@content> tag.-->
<#assign testValue>Some Test Value</#assign> 
<@content 'page.h2'><h2>This is the default content. Here is a test value: ${testValue}</h2></@content>

    After reviewing my options I decided to go with #2 as it worked and should be easy to maintain as long as the Freemarker internal Macro code has package-private access.