Get and format yesterday's date in Camel's expression language

Question

I am using the date in a path in Camel:

fileName=${date:now:dd-MM-yyyy}

but what I need is now - 1 day. Is that possible?

Answer 1

Well, not directly. The date: object in the simple language can only grab the current time (or some time value you have placed inside a header - which you could do in java or similar.

But you could also do like this. Create a class:

public class YesterdayBean{
    public String getYesterday(){
        Calendar cal = Calendar.getInstance();
        DateFormat dateFormat = new SimpleDateFormat("dd-MM-yyyy");
        cal.add(Calendar.DATE, -1); 
        return dateFormat.format(cal.getTime());  
    }
}

Wire it to your Camel (or spring, if you use that) registry as a bean. If you are unsure how to do that, lookup registry and the "using" section of bean.

Let's say you named the bean "yesterday" in the registry, with spring:

<bean id="yesterday" class="some.package.YesterdayBean"/>

then just use it with the file component.

.to("file:fo/bar?fileName=${bean:yesterday}")

If this is just one single place you need it, and you are using Java DSL, you could also just pre-create the date with a java processor and place it in a header.

Like this:

from("file:somewhere")
        .process(new Processor(){
            public void process(Exchange ex){
                Calendar cal = Calendar.getInstance();
                cal.add(Calendar.DATE, -1); 
                ex.getIn().setHeader("yesterday",cal.getTime());
            }
        })
       .to("file:target?fileName=${date:header.yesterday:dd-MM-yyyy}");
}

Answer 2

Camel Simple language date variable supports command with offset:

Supported commands are: now for current timestamp, [...] Command accepts offsets such as: now-24h or header.xxx+1h or even now+1h30m-100.

So you can write your assigment as:

fileName=${date:now-1d:dd-MM-yyyy}

Note that -1d equals to -24h even not mentioned in the documentation.