Java, Threads, and InterruptedException

If you have ever called Thread.sleep and cursed about having to now deal with the InterruptedException, you should read this!

http://www.ibm.com/developerworks/java/library/j-jtp05236/index.html

Java tip: How to list and find threads and thread groups

Found a fantastic post on finding threads and thread groups

http://nadeausoftware.com/articles/2008/04/java_tip_how_list_and_find_threads_and_thread_groups

ResourceBundles and special characters

Seems that some special characters when used in a ResourceBundle proper file will throw off the parser for substitution. These characters need to be escaped properly, the escape notation is as follows:

The special chars \', { and }:

escape ' with another '	''	(double-single quote)
escape \ with another \	\\	(double backslash)
enclose } with '	'}'
enclose { with '	'{'

See also:

• http://struts.apache.org/2.0.14/docs/how-to-escape-special-chars-in-resource-bundles.html

EasyMock: Great tutorial on getting started

http://lijinjoseji.wordpress.com/2009/01/02/creating-mock-tests-using-easy-mock/

Steps to add ssl cert to JVM

Found a great link for adding certs to java for windows, Mac, and linux.

http://eclipse.open.collab.net/servlets/ProjectProcess?pageID=3450

Ignoring Certs for Testing

Had an issue while using XFire (legacy version of CXF), where I needed to access a website using ssl but that had a self-signed cert. The Protocol constructor is depreciated, but for testing purposes works fine.

Example

//protocol=https, etc
protected static void ignoreCertsFor(String protocol, int port){
  Protocol.registerProtocol(protocol, new Protocol(protocol, new EasySSLProtocolSocketFactory(), port));
}

EasySSLProtocolSocketFactory basically uses a "null" implementation of a X509TrustManager.

"null" X509TrustManager Example

new X509TrustManager() {

  public void checkClientTrusted(X509Certificate[] certs, String authType) {
  }

  public void checkServerTrusted(X509Certificate[] certs, String authType) {
  }

  public X509Certificate[] getAcceptedIssuers() {
    return null;
  }
};

See Also:
http://stackoverflow.com/questions/2301548/calling-axis2-web-service-from-xfire-client-the-endpoint-reference-epr-for-the

Sample Java usage for MongoDB

Maven

<dependency>
<groupId>org.mongodb</groupId>
<artifactId>mongo-java-driver</artifactId>
<version>2.5</version>
</dependency>

Connect to Mongo

import com.mongodb.DB;
import com.mongodb.Mongo;

//...

Mongo mongo = new Mongo(host, 27017);
DB db = mongo.getDB("name of db"); //If db does not exist, then it will be created.

Insert JSON Data

import com.mongodb.BasicDBObject;
import com.mongodb.DBCollection;

//...

DBCollection coll = db.getCollection("testCollection"); //If collection does not exist, then it will be created.
BasicDBObject doc = new BasicDBObject();
doc.put("hello", "world");

BasicDBObject inner = new BasicDBObject();
inner.put("key","value");
doc.put("inner", inner);

coll.insert(doc);

Fetch JSON Data

import com.mongodb.BasicDBObject;
import com.mongodb.DBCollection
import com.mongodb.DBCursor;

//...

DBCollection coll = db.getCollection("testCollection");
BasicDBObject query = new BasicDBObject();
query.put("hello", "world");
DBCursor cursor = coll.find(query);
while(cursor.hasNext()) {
System.out.println(cursor.next());
}

GridFS

import com.mongodb.gridfs.GridFS;

//...

GridFS fs = new GridFS(db, "collection"); //If bucket does not exist, it will be created.

GridFS Save File

import java.io.File;
import com.mongodb.gridfs.GridFSInputFile;

//...

GridFSInputFile file = fs.createFile(new File("/path/to/file.ext"));
file.save();

GridFS List Files

import com.mongodb.DBCursor;

//...

DBCursor cursor = fs.getFileList();
while(cursor.hasNext()) {
System.out.println(cursor.next());
}

GridFS Read File

GridFSDBFile file = fs.findOne("file.ext");
BufferedReader reader = new BufferedReader(new InputStreamReader(file.getInputStream()));
String line = null;
while((line = reader.readLine()) != null){
System.out.println(line);
}

Map/Reduce

Example Dataset:
{ "_id" : ObjectId("4d8233d6d638a2ca105b1fab"), "name" : "John", "number" : 2 }
{ "_id" : ObjectId("4d8233d6d638a2ca105b1fac"), "name" : "Jane", "number" : 2 }
{ "_id" : ObjectId("4d8233dbd638e40a183d27f8"), "name" : "John", "number" : 2 }
{ "_id" : ObjectId("4d8233dcd638e40a183d27f9"), "name" : "Jane", "number" : 2 }

Code Example:
import com.mongodb.MapReduceCommand;
import com.mongodb.MapReduceOutput;

//...

String map = "function(){" +
"emit(this.name, {count: 1, sum: this.number});" +
"};";

String reduce = "function( key , values ){" +

"var n = { count: 0, sum: 0}; " +

"for ( var i = 0; i < values.length; i ++ ) {" +

"n.sum += values[i].sum;" +

"n.count += values[i].count;" +

"};" +

"return n;" +

"};";

MapReduceOutput out = coll.mapReduce(map, reduce, null, MapReduceCommand.OutputType.INLINE, null);
for ( DBObject obj : out.results() ) {
System.out.println( obj );
}

Expected Output:
{ "_id" : "Jane" , "value" : { "count" : 2.0 , "sum" : 4.0}}
{ "_id" : "John" , "value" : { "count" : 2.0 , "sum" : 4.0}}

How to build a basic Pax-Runner application with Maven that utilizes spring-dm

My goal is to create a Maven based solution that can automatically assemble a pax-runner driven application that is ready to be deployed.

To make this work with a larger application, there should be an outer pom that includes this and any other bundles as modules. This should be the last module processed, the assembly process will pick up on the other modules built at the same time.

Directory Structure:

• pom.xml
• src
  • main
    • etc
      • assembly
        • paxrunner-assembly.xml
      • scripts
        • run.bat - for windows
        • run.sh - for *nix

To start I created a Maven pom file that has pax-runner as a dependency and references a custom assembly file.

pom.xml

<dependencies>
<dependency>
<groupId>org.ops4j.pax.runner</groupId>
<artifactId>pax-runner</artifactId>
<version>${pax-runner.version}</version>
<scope>provided</scope>
</dependency>
</dependencies>

<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-assembly-plugin</artifactId>
<version>2.2.1</version>
<executions>
<execution>
<id>create-target</id>
<phase>package</phase>
<goals>
<goal>single</goal>
</goals>
<configuration>
<descriptors>
<descriptor>src/main/etc/assembly/paxrunner-assembly.xml</descriptor>
</descriptors>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>

The assembly file will tell Maven how to package the final output. The xml is fairly easy to read, see the maven-assembly-plugin documentation for specifics. The one thing worth calling out is the exclusion of the spring and related libraries, this is because pax-runner already has a built in profile that will download and wire them up properly.

paxrunner-assembly.xml

<assembly xmlns="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.2"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.2 http://maven.apache.org/xsd/assembly-1.1.2.xsd">

<id>distribution</id>

<formats>
<format>dir</format>
<format>zip</format>
</formats>

<includeBaseDirectory>false</includeBaseDirectory>

<files>
<file>
<source>src/main/etc/scripts/run.sh</source>
<fileMode>0777</fileMode>
</file>
<file>
<source>src/main/etc/scripts/run.bat</source>
<fileMode>0777</fileMode>
</file>
</files>

<moduleSets>
<moduleSet>
<binaries>
<unpack>false</unpack>
<includeDependencies>true</includeDependencies>
<outputDirectory>lib/module-bundles</outputDirectory>
<dependencySets>
<!-- 3rd party libraries -->
<dependencySet>
<outputDirectory>lib/required-bundles</outputDirectory>
<excludes>
<exclude>org.springframework:org.springframework.core</exclude>
<exclude>org.springframework:org.springframework.aop</exclude>
<exclude>org.springframework:org.springframework.asm</exclude>
<exclude>org.springframework:org.springframework.beans</exclude>
<exclude>org.springframework:org.springframework.context</exclude>
<exclude>org.springframework:org.springframework.context.support</exclude>
<exclude>org.springframework:org.springframework.expression</exclude>
<exclude>org.slf4j:*</exclude>
<exclude>org.aopalliance:*</exclude>
<exclude>org.apache.commons:*.logging</exclude>
</excludes>
</dependencySet>
</dependencySets>
</binaries>
</moduleSet>
</moduleSets>

<dependencySets>
<!-- Adds pax-runner to root of distribution -->
<dependencySet>
<scope>provided</scope>
<includes>
<include>org.ops4j.pax.runner:pax-runner</include>
</includes>
<outputFileNameMapping>${artifact.artifactId}.${artifact.extension}</outputFileNameMapping>
</dependencySet>
</dependencySets>

</assembly>

Finally for the scripts, these do nothing more than start up pax-runner and pass in any directories of bundles or configuration files.

run.sh

java -jar pax-runner.jar --profiles=spring.dm --workingDirectory=. scan-dir:lib/required-bundles scan-dir:lib/module-bundles

run.bat

@echo off
call java -jar pax-runner.jar --profiles=spring.dm --workingDirectory=. scan-dir:lib/required-bundles scan-dir:lib/module-bundles %1 %2 %3