Java Reflection and the Class Hierarchy - retrieving Fields

Java Reflection and the Class Hierarchy - retrieving Fields

here's a little snippet to keep in mind when trying to identify a field in a possible n tier class hierarchy;

  Class < ? > cls = object.getClass();
  while (true) {
   try {
    field = cls.getDeclaredField(someField);
    break;
   }
   catch (NoSuchFieldException e) {
    cls = cls.getSuperclass();
   }
   catch (Exception e) {
    throw new RuntimeException(e);
   }
  }
  
  field.setAccessible(true); 

.

Setup a Single-Node Hadoop Cluster on Ubuntu

Setup a Single-Node Hadoop Cluster on Ubuntu

a nice step-by-step to setup Hadoop on Ubuntu

http://www.michael-noll.com/tutorials/running-hadoop-on-ubuntu-linux-single-node-cluster/

only thing done differently is the manual install of Java 6 (that ppa doesn't appear to work)

https://help.ubuntu.com/community/Java

JConsole and Unable to see Local Apps

JConsole and Unable to see Local Apps

very strange thing i have come across on occasion with JConsole.  Local apps are only shown as PID's and their greyed out (inaccessible).  i tracked down the solution to it so am sharing here...

in your windows %TEMP% directory, there is a folder called hsperfdata_[userid].  on occasion, Windows pretends to be case sensitive and any letters in your userid need to be in uppercase.  once this is done, restart console and you're good to go

ExecutorService in Spring

ExecutorService in Spring

something i'm always forgetting so i'll put it here to find it again

Maven - Set Compiler Version

i'm always forgetting this...

  
    [...]
    
      
        org.apache.maven.plugins
        maven-compiler-plugin
        2.5.1
        
          1.4
          1.4
        
      
    
    [...]
  

Spring Data JPA & Hibernate & EhCache

Spring Data JPA & Hibernate & EhCache

here's a simple setup to run an EhCache configuration on Spring Data JPA

first the maven

  4.0.0
  org.incomplete.spring
  spring-jpa-cache
  0.0.1-SNAPSHOT
  war
  spring-jpa-cache
  
  	
	  
	    org.apache.maven.plugins
	    maven-compiler-plugin
	    2.3.2
	    
	        1.6
	        1.6
	    
	    	
  	
  
  
  	
  		org.springframework.data
  		spring-data-jpa
  		1.1.0.RELEASE
  	
  	
  		org.hibernate
  		hibernate-entitymanager
  		4.1.4.Final
  	
  	
  		org.hibernate
  		hibernate-validator
  		4.3.0.Final
  	
  	
  		org.hsqldb
  		hsqldb
  		2.2.8
  		test
  	
  	
  		org.springframework
  		spring-test
  		3.1.0.RELEASE
  		test
  	
  	
  		junit
  		junit
  		4.8.2
  		test
  	
  	
  		log4j
  		log4j
  		1.2.14
  	
  	
  		org.slf4j
  		slf4j-log4j12
  		1.6.0
  	
  	
  		net.sf.ehcache
  		ehcache-core
  		2.6.0
  	
  	
  		org.hibernate
  		hibernate-ehcache
  		4.1.4.Final
  	
  

then our basic entity

package org.incompletecode.spring.domain;
 
import java.io.Serializable;
 
import javax.persistence.Cacheable;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;
import javax.persistence.Transient;
 
@Cacheable
@Entity
@Table(name="simple_entity")
public class SimpleEntity implements Serializable {
 
	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;
 
	@Id
	@GeneratedValue(strategy=GenerationType.AUTO)
	private Long id;
	
	@Column
	private String name;
	
	@Column
	private String description;
 
	public Long getId() {
		return id;
	}
 
	public void setId(Long id) {
		this.id = id;
	}
 
	public String getName() {
		return name;
	}
 
	public void setName(String name) {
		this.name = name;
	}
 
	public String getDescription() {
		return description;
	}
 
	public void setDescription(String description) {
		this.description = description;
	}
 
	@Override
	@Transient
	public String toString() {
		return "SimpleEntity [id=" + id + ", name=" + name + ", description="
				+ description + "]";
	}
	
	
	
}

our DAO

package org.incompletecode.spring.dao;
 
import org.incompletecode.spring.domain.SimpleEntity;
import org.springframework.data.jpa.repository.JpaRepository;
 
public interface SimpleEntityDAO extends JpaRepository< SimpleEntity, Long > {
 
}

now our Spring Config for the key parts (Spring Data, JPA, Transaction Manager)

 
	
	
	
 
	
		
		
		
			
				
					
		
		
			
				org.hibernate.cache.SingletonEhCacheProvider
				/META-INF/cache/ehcache.xml
				true
				true
				org.hibernate.cache.ehcache.EhCacheRegionFactory
			
		
	
 
	
		
		
	
	

and of course our database stuff

the cache config

and now for a unit test

package org.incompletecode.spring.dao;
 
import static org.junit.Assert.assertNotNull;
 
import java.util.ArrayList;
import java.util.List;
 
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.hsqldb.jdbc.JDBCDataSource;
import org.incompletecode.spring.domain.SimpleEntity;
import org.junit.After;
import org.junit.Before;
import org.junit.BeforeClass;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.mock.jndi.SimpleNamingContextBuilder;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.util.StopWatch;
 
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration({"classpath:/META-INF/spring/data-context.xml",
	"classpath:/META-INF/spring/datasource-context.xml"})
public class SimpleEntityDAOTest {
 
	private static final Log logger = LogFactory.getLog(SimpleEntityDAOTest.class);
	
	public static final int count = 10000;
	
	@Autowired
	private SimpleEntityDAO simpleEntityDAO;
	
	private StopWatch stopWatch = new StopWatch();
	
	@BeforeClass
	public static void beforeClass() throws Exception {
		SimpleNamingContextBuilder builder = SimpleNamingContextBuilder.emptyActivatedContextBuilder();
		//build
		JDBCDataSource dataSource = new JDBCDataSource();
		dataSource.setUrl("jdbc:hsqldb:mem:a");
		//bind
		builder.bind("jdbc/datasource", dataSource);
	}
	
	@Before
	public void before() throws Exception {
		List< SimpleEntity > simpleEntities = new ArrayList< SimpleEntity >(count);
		//create a list
		stopWatch.start();
		for (int i=0; i< count; i++) {
			SimpleEntity simpleEntity = new SimpleEntity();
			simpleEntity.setName("code" + i);
			simpleEntities.add(simpleEntity);
		}//end for
		stopWatch.stop();
		logger.info("time to create: " + stopWatch.getLastTaskTimeMillis() + "ms");
		//save
		stopWatch.start();
		simpleEntityDAO.save(simpleEntities);
		stopWatch.stop();
		logger.info("time to save: " + stopWatch.getLastTaskTimeMillis() + "ms");
	}
	
	@After
	public void after() throws Exception {
		stopWatch.start();
		simpleEntityDAO.deleteAllInBatch();
		stopWatch.stop();
		logger.info("time to delete in batch: " + stopWatch.getLastTaskTimeMillis() + "ms");
	}
	
	@Test
	public void test() throws Exception {
		//create an entity
		SimpleEntity simpleEntity = new SimpleEntity();
		simpleEntity.setName("hi");
		//save
		simpleEntityDAO.save(simpleEntity);
		//check
		assertNotNull(simpleEntity.getId());
	}
	
	@Test
	public void testRetrieveAll() throws Exception {
		stopWatch.start();
		simpleEntityDAO.findAll();
		stopWatch.stop();
		logger.info("time to retrieve all: " + stopWatch.getLastTaskTimeMillis() + "ms");
	}
	
	@Test
	public void testMultipleRetrieveAll() throws Exception {
		for (int i=0;i<10;i++) {
			testRetrieveAll();
		}
	}
	
}

here's some stats on the unit test above; running it on my local machine inside STS, i can squeeze a 20% performance improvement with caching enabled.  not too shabby

Maven - Setting Code Version

Maven - Setting Code Version

i keep forgetting this, so i'm putting it here; how to set the code version in maven build scripts

A Java Tree Object

here's a useful link on how to build your own tree object using Generics... old but useful

http://www.java2s.com/Tutorial/Java/0200__Generics/Yourowntreewithgenericuserobject.htm

java.util.Date to XmlGregorianCalendar

a little thing i keep forgetting so i'm putting it here...

Java 6 End Of Life - Nov 2012

here's the source...

http://www.oracle.com/technetwork/java/eol-135779.html