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new 404cce386a9c CAMEL-22899: camel-core - Simple language chain operator
to support for explicit declaring input parameter position
404cce386a9c is described below
commit 404cce386a9c9c62d5de5c890e81191294e3612d
Author: Claus Ibsen <[email protected]>
AuthorDate: Thu Jan 29 16:19:50 2026 +0100
CAMEL-22899: camel-core - Simple language chain operator to support for
explicit declaring input parameter position
---
.../modules/languages/pages/simple-language.adoc | 22 +++++++++--
.../camel/language/simple/ast/ChainExpression.java | 45 +++++++++++++++++++++-
.../camel/language/simple/SimpleOperatorTest.java | 11 ++++++
3 files changed, 73 insertions(+), 5 deletions(-)
diff --git
a/core/camel-core-languages/src/main/docs/modules/languages/pages/simple-language.adoc
b/core/camel-core-languages/src/main/docs/modules/languages/pages/simple-language.adoc
index ba44eb8dee2a..6cbc590598de 100644
---
a/core/camel-core-languages/src/main/docs/modules/languages/pages/simple-language.adoc
+++
b/core/camel-core-languages/src/main/docs/modules/languages/pages/simple-language.adoc
@@ -867,9 +867,6 @@ simple("${header.username} ?: 'Guest'");
==== Chain Operator
-IMPORTANT: The chain operator only supports passing results via the message
body. This may change in the future to allow more flexible syntax to
-specify which parameter to use as input in the next fuction.
-
The syntax for the chain operator is:
[source,text]
@@ -895,6 +892,25 @@ The _null safe_ variant (`?~>`) can be used to avoid
`NullPointerException` if i
However, many of the simple functions have NPE protection built-in, so this
variant is only needed in special situations.
+==== Using $param as input parameter value
+
+IMPORTANT: The chain operator will by default pass results via the message
body. This usually works well with most functions.
+However, when you need to be in full control then use `$param` as the magic
parameter which represents the passed value from the previous function in the
chain.
+
+Suppose the message body contains `" Hello World from the Camel "` then the
following chain works out of the box:
+
+[source,java]
+----
+simple("${trim()} ~> ${replace('Hello','Hi')} ~> ${split(' ')} ~> ${size()}");
+----
+
+And here is the same example where we explicit use `$param` in the parameters
where we need the input to be:
+
+[source,java]
+----
+simple("${trim()} ~> ${replace('Hello','Hi',$param)} ~> ${split($param,' ')}
~> ${size($param)}");
+----
+
=== Boolean Operators
diff --git
a/core/camel-core-languages/src/main/java/org/apache/camel/language/simple/ast/ChainExpression.java
b/core/camel-core-languages/src/main/java/org/apache/camel/language/simple/ast/ChainExpression.java
index 955843346854..fcbcb64d6977 100644
---
a/core/camel-core-languages/src/main/java/org/apache/camel/language/simple/ast/ChainExpression.java
+++
b/core/camel-core-languages/src/main/java/org/apache/camel/language/simple/ast/ChainExpression.java
@@ -27,6 +27,7 @@ import org.apache.camel.language.simple.BaseSimpleParser;
import org.apache.camel.language.simple.types.ChainOperatorType;
import org.apache.camel.language.simple.types.SimpleParserException;
import org.apache.camel.language.simple.types.SimpleToken;
+import org.apache.camel.support.ExpressionAdapter;
import org.apache.camel.util.ObjectHelper;
import org.apache.camel.util.StringHelper;
@@ -35,6 +36,8 @@ import org.apache.camel.util.StringHelper;
*/
public class ChainExpression extends BaseSimpleNode {
+ private static final String CHAIN_VARIABLE = "CamelSimpleChainParam";
+
private final ChainOperatorType operator;
private SimpleNode left;
private final List<SimpleNode> right = new ArrayList<>();
@@ -86,15 +89,53 @@ public class ChainExpression extends BaseSimpleNode {
final List<Expression> rightExp = new ArrayList<>();
for (SimpleNode rn : right) {
+ boolean param = false;
if (rn instanceof LiteralExpression le) {
String text = le.getText();
String changed =
StringHelper.removeLeadingAndEndingQuotes(text);
+ if (changed.contains("$param")) {
+ changed = changed.replace("$param", "${variable." +
CHAIN_VARIABLE + "}");
+ param = true;
+ }
if (!changed.equals(text)) {
le.replaceText(changed);
}
+ } else if (rn instanceof SimpleFunctionStart sf) {
+ for (var child : sf.getBlock().getChildren()) {
+ if (child instanceof LiteralExpression le) {
+ String text = le.getText();
+ String changed =
StringHelper.removeLeadingAndEndingQuotes(text);
+ if (changed.contains("$param")) {
+ changed = changed.replace("$param", "${variable."
+ CHAIN_VARIABLE + "}");
+ param = true;
+ }
+ if (!changed.equals(text)) {
+ le.replaceText(changed);
+ }
+ }
+ }
+ }
+ final Expression exp = rn.createExpression(camelContext,
expression);
+ Expression target = exp;
+ if (param) {
+ target = new ExpressionAdapter() {
+ @Override
+ public Object evaluate(Exchange exchange) {
+ exchange.setVariable(CHAIN_VARIABLE,
exchange.getMessage().getBody());
+ try {
+ return exp.evaluate(exchange, Object.class);
+ } finally {
+ exchange.removeVariable(CHAIN_VARIABLE);
+ }
+ }
+
+ @Override
+ public String toString() {
+ return exp.toString();
+ }
+ };
}
- Expression exp = rn.createExpression(camelContext, expression);
- rightExp.add(exp);
+ rightExp.add(target);
}
if (operator == ChainOperatorType.CHAIN || operator ==
ChainOperatorType.CHAIN_NULL_SAFE) {
diff --git
a/core/camel-core/src/test/java/org/apache/camel/language/simple/SimpleOperatorTest.java
b/core/camel-core/src/test/java/org/apache/camel/language/simple/SimpleOperatorTest.java
index 5effdce5234d..cb8807a94108 100644
---
a/core/camel-core/src/test/java/org/apache/camel/language/simple/SimpleOperatorTest.java
+++
b/core/camel-core/src/test/java/org/apache/camel/language/simple/SimpleOperatorTest.java
@@ -951,6 +951,17 @@ public class SimpleOperatorTest extends
LanguageTestSupport {
assertTrue(matches);
}
+ @Test
+ public void testChainParam() {
+ exchange.getIn().setBody(" Hello World from the Camel ");
+ // no param
+ assertExpression("${trim()} ~> ${replace('Hello','Hi')}", "Hi World
from the Camel");
+ assertExpression("${trim()} ~> ${replace('Hello','Hi')} ~> ${split('
')} ~> ${size()}", 5);
+ // with $param
+ assertExpression("${trim()} ~> ${replace('Hello','Hi',$param)}", "Hi
World from the Camel");
+ assertExpression("${trim()} ~> ${replace('Hello','Hi',$param)} ~>
${split($param,' ')} ~> ${size($param)}", 5);
+ }
+
@Override
protected String getLanguageName() {
return "simple";
