dynamic template generation and formatting using freemarker - spring-integration

Question

My goal is to format a collection of java map to a string (basically a csv) using free marker or anything else that would do smartly. I want to generate the template using a configuration data stored in database and managed from an admin application.
The configuration will tell me at what position a given data (key in hash map) need to go and also if any script need to run on this data before applying it at a given position. Several positions may be blank if the data in not in map.
I am thinking to use free-marker to build this generic tool and would appreciate if you could share how I should go about this.
Also would like to know if there is any built is support in spring-integration for building such process as the application is a SI application.

Answer 1

I am no freemarker expert, but a quick look at their quick start docs led me here...
public class FreemarkerTransformerPojo {
private final Configuration configuration;
private final Template template;
public FreemarkerTransformerPojo(String ftl) throws Exception {
this.configuration = new Configuration(Configuration.VERSION_2_3_23);
this.configuration.setDirectoryForTemplateLoading(new File("/"));
this.configuration.setDefaultEncoding("UTF-8");
this.template = this.configuration.getTemplate(ftl);
}
public String transform(Map<?, ?> map) throws Exception {
StringWriter writer = new StringWriter();
this.template.process(map, writer);
return writer.toString();
}
}
and
public class FreemarkerTransformerPojoTests {
#Test
public void test() throws Exception {
String template = System.getProperty("user.home") + "/Development/tmp/test.ftl";
OutputStream os = new FileOutputStream(new File(template));
os.write("foo=${foo}, bar=${bar}".getBytes());
os.close();
FreemarkerTransformerPojo transformer = new FreemarkerTransformerPojo(template);
Map<String, String> map = new HashMap<String, String>();
map.put("foo", "baz");
map.put("bar", "qux");
String result = transformer.transform(map);
assertEquals("foo=baz, bar=qux", result);
}
}
From a Spring Integration flow, send a message with a Map payload to
<int:transformer ... ref="fmTransformer" method="transform" />
Or you could do it with a groovy script (or other supported scripting language) using Spring Integration's existing scripting support without writing any code (except the script).