Standalone Apache Camel with Spring tutorial -- file transformer

In the last Apache Camel with Spring tutorial we went through polling a folder for a file pattern, and then zip and copy the file to the archive subfolder. This tutorial extends that to show how we can read a file say test1.csv in the format shown below

firstname,surname, age
John, Smith, 35
Peter, Smith, 25

and then convert it to a format shown below where fields firstname and surname are swapped.

surname,firstname,age
Smith,John,35
Smith,Peter,25

Step 1: Add camel-csv dependency to the pom.xml file that enables reading csv files

     <dependency>
   <groupId>org.apache.camel</groupId>
   <artifactId>camel-csv</artifactId>
   <version>2.10.4</version>
  </dependency>

Step 2: The next step is to define the routes in the simple_file_route.xml file.

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
 xmlns:p="http://www.springframework.org/schema/p" xmlns:c="http://www.springframework.org/schema/c"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:camel="http://camel.apache.org/schema/spring"
 xsi:schemaLocation="
  http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/camel-spring.xsd">

 <routeContext id="simpleFileRoute" xmlns="http://camel.apache.org/schema/spring">
  <route id="fileIn">
   <from
    uri="file://c:/temp/simple/input?include=test.*csv&delay=600000&initialDelay=5000" />

   <unmarshal>
    <csv skipFirstLine="true" />
   </unmarshal>
   <to uri="bean:personMapper" />
   <marshal>
    <csv delimiter="," />
   </marshal>
   <convertBodyTo type="java.lang.String" />
   <to uri="file://c:/temp/simple/output?fileName=${file:name.noext}_new.csv" />
  </route>
 </routeContext>
</beans>

Step 3: The above route uses the "PersonMapper" bean class to transform the fields. This is basically translating the file by rearranging "surname" and "firstname" columns.

package com.mycompany.app3;

import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

import org.springframework.stereotype.Component;

@Component("personMapper")
public class PersonMapper
{
    
    public Object service(List<List<String>> data)
    {
        List<Map<String, String>> results = new ArrayList<Map<String, String>>();
        
        Map<String, String> headerLine = new LinkedHashMap<String, String>();
        headerLine.put("surname", "surname");
        headerLine.put("firstname", "firstname");
        headerLine.put("age", "age");
        
        results.add(headerLine);
        
        for (List<String> line : data)
        {
            Map<String, String> resultLine = new LinkedHashMap<String, String>();
            resultLine.put("surname", line.get(1));
            resultLine.put("firstname", line.get(0));
            resultLine.put("age", line.get(2));
            results.add(resultLine);
        }
        
        return results;
        
    }
}

That's all to it. This is the power of the integration framework Apache Camel. It supports 20+ protocols like ftp, smtp, etc.