CSimple

Since Camel 3.7

The CSimple language is compiled Simple language.

Different between CSimple and Simple

The simple language is a dynamic expression language which is runtime parsed into a set of Camel Expressions or Predicates.

The csimple language is parsed into regular Java source code and compiled together with all the other source code, or compiled once during bootstrap via the camel-csimple-joor module.

The simple langauge is generally very lightweight and fast, however for some use-cases with dynamic method calls via OGNL paths, then the simple language does runtime introspection and reflection calls. This has an overhead on performance, and was one of the reasons why csimple was created.

The csimple language requires to be typesafe and method calls via OGNL paths requires to know the type during parsing. This means for csimple languages expressions you would need to provide the class type in the script, where as simple introspects this at runtime.

In other words the simple language is using duck typing (if it looks like a duck, and quacks like a duck, then it is a duck) and csimple is using Java type (typesafety). If there is a type error then simple will report this at runtime, and with csimple there will be a Java compilation error.

Compilation

The csimple language is parsed into regular Java source code and compiled together with all the other source code, or it can be compiled once during bootstrap via the camel-csimple-joor module.

There are two ways to compile csimple

using the camel-csimple-maven-plugin generating source code at built time.
using camel-csimple-joor which does runtime in-memory compilation during bootstrap of Camel.

Using camel-csimple-maven-plugin

The camel-csimple-maven-plugin Maven plugin is used for discoving all the csimple scripts from the source code, and then automatic generate source code in the src/generated/java folder, which then gets compiled together with all the other sources.

The maven plugin will do source code scanning of .java and .xml files (Java and XML DSL). The scanner limits to detect certain code patterns, and it may miss discovering some csimple scripts if they are being used in unusual/rare ways.

The runtime compilation using camel-csimple-joor does not have this limitation.

However the pros is that all of the csimple scripts will be compiled using the regular Java compiler and therefore everything is included out of the box as .class files in the application JAR file, and no additional dependencies is required at runtime.

To use camel-csimple-maven-plugin you need to add it to your pom.xml file as shown:

<plugins>
    <!-- generate source code for csimple languages -->
    <plugin>
        <groupId>org.apache.camel</groupId>
        <artifactId>camel-csimple-maven-plugin</artifactId>
        <version>${camel.version}</version>
        <executions>
            <execution>
                <id>generate</id>
                <goals>
                    <goal>generate</goal>
                </goals>
            </execution>
        </executions>
    </plugin>
    <!-- include source code generated to maven sources paths -->
    <plugin>
        <groupId>org.codehaus.mojo</groupId>
        <artifactId>build-helper-maven-plugin</artifactId>
        <version>3.1.0</version>
        <executions>
            <execution>
                <phase>generate-sources</phase>
                <goals>
                    <goal>add-source</goal>
                    <goal>add-resource</goal>
                </goals>
                <configuration>
                    <sources>
                        <source>src/generated/java</source>
                    </sources>
                    <resources>
                        <resource>
                            <directory>src/generated/resources</directory>
                        </resource>
                    </resources>
                </configuration>
            </execution>
        </executions>
    </plugin>
</plugins>

And then you must also add the build-helper-maven-plugin Maven plugin to include src/generated to the list of source folders for the Java compiler, to ensure the generated source code is compiled and included in the application JAR file.

See the camel-example-csimple example at Camel Examples which uses the maven plugin.

Using camel-csimple-joor

The jOOR library integrates with the Java compiler and performs runtime compilation of Java code.

The supported runtime when using camel-simple-joor is intended for Java standalone, Spring Boot, Camel Quarkus and other microservices runtimes. It is not supported in OSGi, Camel Karaf or any kind of Java Application Server runtime.

jOOR does not support runtime compilation with Spring Boot using fat jar packaging (https://github.com/jOOQ/jOOR/issues/69), it works with exploded classpath.

To use camel-simple-joor you simply just add it as dependency to the classpath:

<dependency>
  <groupId>org.apache.camel</groupId>
  <artifactId>camel-csimple-joor</artifactId>
  <version>x.x.x</version>
</dependency>

There is no need for adding Maven plugins to the pom.xml file.

See the camel-example-csimple-joor example at Camel Examples which uses the jOOR compiler.

CSimple Language options

The CSimple language supports 2 options, which are listed below.

Name Default Java Type Description

Name	Default	Java Type	Description
resultType		`String`	Sets the class name of the result type (type from output)
trim	`true`	`Boolean`	Whether to trim the value to remove leading and trailing whitespaces and line breaks

resultType

String

Sets the class name of the result type (type from output)

trim

true

Boolean

Whether to trim the value to remove leading and trailing whitespaces and line breaks

Limitations

Currently the csimple language does not support the null safe operator (?).

For example the following script cannot compile:

    ${bodyAs(MyUser)?.address?.zip} > 10000