Converting Ant to Maven in NetBeans

After a good couple of days spent converting ant projects over to maven, here is what I consider the easiest method. This is using NetBeans 6.5rc1 but probably works in 6.1.

Here are the steps for converting an ant project to a maven project in NetBeans.
This presumes your ~/.m2/settings.xml is already set up (not shown here for security purposes) and you have installed the Netbeans maven2 plugin:

1. Open ant project
2. Create new maven project using the “Maven Quickstart Archetype”
3. Properties -> Sources -> Change to 1.6
4. pom.xml -> Add distribution management

<distributionManagement>
  <repository>
    <id>nexus</id>
    <name>Internal Releases</name>
    <url>YourInternalReleaseURL</url>
  </repository>
</distributionManagement>

5. Files tab -> src/main -> add folder “resources”. This will create an “Other Sources/resources” entry in the project view
6. Delete existing source and test package stubs
7. Copy java sources and test sources across from ant project
8. Move all config xml files (such as applicationContext.xml) over to “Other Sources/resources”
9. If you have any hibernate .hbm.xml files, create a folder structure under “Other Sources/resources” identical to the package structure, and copy the files to there
10. Resolve dependencies. The easiest way to do this is go through red-underlined classes, copy the missing required classname, right-click the libraries node and hit “Find Dependency”
11. If a dependency is purely for a test class, add “<scope>test</scope>” to reduce the resulting jar filesize
12. mvn install or deploy

If the ant project exposes a WebService:
1. Add the following plugin to the pom.xml:

<plugin>
  <groupId>org.codehaus.mojo</groupId>
  <artifactId>jaxws-maven-plugin</artifactId>
  <executions>
    <execution>
      <goals>
        <goal>wsimport</goal>
      </goals>
      <configuration>
        <wsdlUrls>
          <wsdlUrl>yourWSDLExposedUrl</wsdlUrl>
        </wsdlUrls>
        <packageName>yourWSClientPackageName</packageName>
        <sourceDestDir>${basedir}/src/main/java</sourceDestDir>
      </configuration>
    </execution>
  </executions>
</plugin>

2. Change the wsdl location and packageName as necessary. Without the sourceDestDir, the generated sources live under target/ and code completion won’t work. Setting the package name to the same package as the ws-client solves this. Compilation works either way.

ehcache and spring

As used by Hibernate, ehcache is a great little caching implementation which ought to be part of every Java coders arsenal. Although its complexities may seem overwhelming, it’s very easy to use as a simple caching solution.

In my situation, I needed to prevent db hits when validating codes (ie seeing if they already exist in the db). This is how easy it is to set up.

applicationContext.xml:

<bean id="myDao" class="myDaoImpl" init-method="setupCache">
  <property name="cacheManager" ref="cacheManager">
</bean>

<bean id="cacheManager" class="org.springframework.cache.ehcache.EhCacheManagerFactoryBean">
  <property name="configLocation" value="classpath:ehcache.xml" />
</bean>

ehcache.xml:

<ehcache>
  <diskStore path="java.io.tmpdir"/>
  <cache name="myCacheName"
    maxElementsInMemory="1000"
    eternal="true"
    overflowToDisk="false"/>
  <defaultCache
    maxElementsInMemory="300"
    maxElementsOnDisk="1000"
    eternal="false"
    timeToIdleSeconds="120"
    timeToLiveSeconds="120"
    overflowToDisk="true"/>
</ehcache>

myDaoImpl.java:

import net.sf.ehcache.Cache;
import net.sf.ehcache.CacheManager;
import net.sf.ehcache.Element;

public class {
  private CacheManager cacheManager;
  private Cache myCache = null;

  public void setCacheManager(CacheManager cacheManager) {
    this.cacheManager = cacheManager;
  }

  private void setupCache() {
    String cacheName = "myCacheName";
    logger.debug("Fetching cache [" + cacheName + "]");
    myCache = cacheManager.getCache(cacheName);
  }
}

ehcache.xml needs to be put alongside applicationContext.xml (especially in the case of jar packaging). If you’re packaging a war, you can place it anywhere on the classpath and don’t need to specify the configLocation (it’s the default config name).

To use the cache, do something like this:

Element cachedObject = myCache.get(key);
if (cachedObject != null) {
  return cachedObject;
} else {
  fetch object from db
  // add to cache
  myCache.put(new Element(key, object))
  return object;
}

And that's it!

Now you’ll only hit the db when needed. Of course, it’s worth reading the reference material to see the many ways you can configure the cache. My example is purely for a 1000 object permanent memory cache, but TTL and overflow-to-disk (for example) is just as easy to set up.