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Custom Functions

Custom functions allow you to extend the Velocity template with Java methods callable from within the template. They are provided by a class that extends com.cefriel.template.utils.TemplateFunctions from the mapping-template library.

There are two mutually exclusive ways to provide custom functions. You cannot use both simultaneously.

Option 1: In-Project Class (customFunctions)

Use this when the custom functions class is compiled as part of your project.

Define a class extending TemplateFunctions:

public class MyFunctions extends TemplateFunctions {
    public String greet(String name) {
        return "Hello, " + name;
    }
}

Reference it in the endpoint:

from("direct:start")
    .to("mapt://?template=#bean:template&customFunctions=#class:com.example.MyFunctions");

- route:
    from: "direct:start"
    steps:
      - to:
          uri: "mapt://"
          parameters:
            template: "#template"
            customFunctions: "#class:com.example.MyFunctions"

Option 2: External Java File (resourceCustomFunctions)

Use this when the custom functions are provided as an external .java file that is compiled at runtime.

ChimeraResourceBean functions = new ChimeraResourceBean(
    "file://./functions/CustomFunctions.java", "java");
getCamelContext().getRegistry().bind("functions", functions);

from("direct:start")
    .to("mapt://?template=#bean:template&resourceCustomFunctions=#bean:functions");

- beans:
    - name: functions
      type: com.cefriel.util.ChimeraResourceBean
      properties:
        url: "file://./functions/CustomFunctions.java"
        serializationFormat: "java"

- route:
    from: "direct:start"
    steps:
      - to:
          uri: "mapt://"
          parameters:
            template: "#template"
            resourceCustomFunctions: "#functions"

Warning

Runtime compilation requires a JDK (not just a JRE) to be available, since it uses javax.tools.JavaCompiler.

The external .java file must define a class named CustomFunctions that extends TemplateFunctions.