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https://issues.apache.org/jira/browse/CAMEL-7831?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14635183#comment-14635183
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christian ohr edited comment on CAMEL-7831 at 7/21/15 3:23 PM:
---------------------------------------------------------------
Predicate and Processor can be implemented with lambdas or function references,
but Expressions cannot.
Lambdas can only implement an interface fully known at compile-time, but
Expression#evaluate is generic.
As of now, one requires a bridge, like this:
{code}
private <V> Expression function(Function<Exchange, V> function) {
return new ExpressionBridge<>(function);
}
private class ExpressionBridge<V> implements Expression {
private final Function<Exchange, V> function;
public ExpressionBridge(Function<Exchange, V> function) {
this.function = function;
}
@Override
public <T> T evaluate(Exchange exchange, Class<T> type) {
return exchange.getContext().getTypeConverter().convertTo(type,
function.apply(exchange));
}
}
{code}
Then you can go ahead and use in your route something like:
{code}
from("direct:blorg")
.transform(function(exchange -> exchange.getProperty("some
prop")))
.to("direct:gablorg");
{code}
was (Author: christian.ohr):
Predicate and Processor can be implemented with lambdas or function references,
but Expressions cannot.
Lambdas can only implement an interface fully known at compile-time, but
Expression#evaluate is generic.
As of now, one requires a bridge, like this:
{code}
private <V> Expression function(Function<Exchange, V> function) {
return new ExpressionBridge<>(function);
}
private class ExpressionBridge<V> implements Expression {
private final Function<Exchange, V> function;
public ExpressionBridge(Function<Exchange, V> function) {
this.function = function;
}
@Override
public <T> T evaluate(Exchange exchange, Class<T> type) {
return exchange.getContext().getTypeConverter().convertTo(type,
function.apply(exchange));
}
}
{code}
> create a java8 only demo showing how to use lambda expressions for Predicate
> / Expression inside the Java DSL (using Message as a typesafe parameter)
> -----------------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: CAMEL-7831
> URL: https://issues.apache.org/jira/browse/CAMEL-7831
> Project: Camel
> Issue Type: New Feature
> Components: examples
> Reporter: james strachan
> Fix For: 2.16.0
>
>
> e.g. so folks can type things like
> {code}
> from("seda:cheese").
> filter(m -> m.getHeader("foo", int.class) > 5).
> map(m -> createPurchaseOrder(m.getBody(Invoice.class)).
> to("seda:bar");
> {code}
> Note if the current Predicate/Expression classes don't work as lambdas we
> could add a new interface with a single method to the DSL to ensure Java 8
> does the right thing with lambdas
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