Shindig communication

 

There are different ways a gadget can interact with the container and vice versa.

1. RPC
2. Gadget to server communication
3. Publish / Subscribe

 RPC

The RPC mechanism is used to perform Gadget to Container communication & Gadget to Gadget communication.

The following needs to be done in order to call an RPC service from a gadget:

Container Page:

§  Create a new javascript Function

§  Register the function as a javascript service using gadgets.rpc.register API.

                Gadget Page:

§  From the gadget, call the RPC service using gadgets.rpc.call API

The first parameter “” indicates that we are going to call arpc service of the parent container.

Define the callback method for processSearchTerm.

1.2.    Gadget to Server communication.

Gadget.io API provides a mechanism by which the gadget will be able to communicate with the server side.

Gadgets.io.makeRequest accepts 3 parameters.

The first param is the URI that defines a service, second one defines the callback method, and the third one is the input parameters to the service.  The content type mentioned in the parameter is given as “TEXT”, which means the service will return a TEXT. The other content types supported are DOM, FEED & JSON. This has been explained in detail here: http://code.google.com/apis/gadgets/docs/remote-content.html#Content_Types

In the above example, the uri - rest/searchResults is nothing but a REST based service defined in Wink.

The code is given below:

           

1.3.    Publish/Subscribe.

This works on the basic bulletin board concept. A gadget can publish a message and the other gadgets which has subscribed for it can obtain the information and perform some business logic.

The example given below is taken from Shindig and is part of the distribution:

Subscriber:

The gadget can subscribe to master gadget using the subscribe API. The first parameter “random-number” defines a channel which it listens to.

The master gadget publishes a message using the following API:

Once this is called, the message is published to the channel, and the callback method is called on the subscriber.

Apache Shindig - Getting started

Shindig Environment Setup (Running the example)

Software installation

There are 2 ways of setting up the Shindig environment:

1.       Directly downloading the shindig war file

§  Download Shindig war from the url: http://shindig.apache.org/download/index.html (shindig-server-1.1-BETA5-incubating.war). Download the latest war.

§  Deploy it in the App Server.

(OR) 

if you want to build from source

2.     From source.

Download Shindig source from the url:http://shindig.apache.org/download/index.html (shindig-1.1-BETA5-incubating-source.zip)

§  Download Apache Maven

§  Ensure JDK 6 is installed in the machine.

§  Set the path to JDK and Maven.

§  Build the war file out of the source using the following command.

mvn install -Dmaven.test.skip=true

Note: We were getting some compilation errors on the test classes hence ensure that we build using the above command.

§  The WAR file would be generated – place where it is built will be mentioned at the end of running the build.

§  Deploy the WAR in the App server.

Note: Deploying the war file:

Tomcat: deploy the war in the webapps directory, rename the war to ROOT.war and restart the server.

JBoss: deploy the war in the server/default/deploy directory, rename the war to ROOT.war and restart the server.

Invoke the following url to ensure that the application is properly installed.

http://localhost:8080/gadgets/files/container/sample1.html. 

Developing Gadgets

Steps:

§  Choose the gadget type – HTML or URL

§  Develop the gadget as defined in this section.

§  Place it in a location where it can be identified by an URI.

§  Develop the container code (which displays these gadgets)

§  Develop miscellaneous services like communication between container, gadget and server depending on your requirement.

Writing a simple Gadget (HTML): 

Code to display the gadget: 

The following were done in the above code:

§  Get the location of the gadget xml

§  Set the layout for the gadget container.

§  Create and add the gadget.

§  Render the gadget using the renderGadgets() API.

Writing a simple Gadget (URL): 

Just mention the url name in the attribute “href” instead of the html content.

There is no change in the way we display the URL type gadget. It follows the same step as we followed in the previous section. 

Apache shindig - Overview

Shindig is an open source framework from Apache that acts as a container for gadgets. iGoogle is built using this framework.

So what is a gadget:

Gadgets are mini applications (similar to portlet) that are written in HTML, Javascript& XML. Gadgets are iframes that are rendered into your web page. 

Date and time gadget, weather gadget, are all shindig gadgets.

These gadgets can interact with the page, communicate between gadgets.

The developer normally writes the gadget as HTML written within the gadget XML. Gadget server processes these XML and converts them into html snippets and displays them as iframe in the web page.

Types of Gadgets:

§  HTML gadgets

This is a type of gadget where the content of the gadget (html) resides within the gadget XML.

§  URL type gadgets

This is a type of gadget where the content of the gadget resides in a third party server. The URI is given as an attribute in the xml.

What is a gadget Container

It is the context where the gadget is embedded. In developer terms it is the page where the gadget resides. The page has some javascript APIs which inturn interacts with the Gadget server for rendering, communicating etc.,

What you can do using Shindig.

Shindig acts as a container for the gadgets. The gadget can perform the following using Shindig

-          Communicate with other gadgets using pub/sub feature.

-          Communicate with the container using RPC.

-          Communicate with server using gadget.io

-          Obtain open social information using the Open social API. 

How can i develop my own gadgets.

Click here to find out how to create your own gadgets.

Some reference links:

§  Shindig home page: http://incubator.apache.org/shindig/index.html

§  Shindig download URL: http://incubator.apache.org/shindig/download/index.html

§  Gadget Dev guide: http://code.google.com/apis/gadgets/docs/dev_guide.html

§  Gadgets API reference: http://code.google.com/apis/gadgets/docs/reference/

§  Gadgets XML reference: http://code.google.com/apis/gadgets/docs/reference.html#Moduleprefs_Ref

§  Open social specification: http://www.opensocial.org/Technical-Resources/opensocial-spec-v09/OpenSocial-Specification.html

§  JavaScript API Reference: http://incubator.apache.org/shindig/shindig-1.1.x/shindig-features/jsdoc/index.html

Word / Sentence detector using opennlp

OpenNLP is a machine learning toolkit used for processing NLP. This article focuses on setting up a simple maven project and runs a simple program using OpenNLP:

Add the following in the maven configuration:

              <!-- Open NLP -->

              <dependency>

                  <groupId>org.apache.opennlp</groupId>

                  <artifactId>opennlp-tools</artifactId>

                  <version>1.5.3</version>

              </dependency>

             

              <dependency>

                  <groupId>commons-io</groupId>

                  <artifactId>commons-io</artifactId>

                  <version>2.4</version>

              </dependency>

Write a java program for getting sentences:

Following are the high level steps:

• Get a reference of the model en-sent.bin using the InputStream
• Create Sentence model and SentenceDetector for the input model stream.
• Get the sentence array using open nlp api

public class SentenceDetectorClient {

       public static void main(String[] args) {

              new SentenceDetectorClient().go();

       }

       private void go() {

              try {

                     InputStream modelIn = new FileInputStream("src/main/resources/models/en-sent.bin");  // --- Import en-sent.bin feil for sentence mich

                     SentenceModel sModel = new SentenceModel(modelIn);

                    

                     SentenceDetectorME sentenceDetector = new SentenceDetectorME(sModel); // ------ Creating a Sentence detector based on the input stream

                    

                     String articleText = "Chris Gayle on Monday sounded out a warning to the rival teams ahead of the World Twenty20 by declaring that he can score a hundred irrespective of the conditions. “I am capable of scoring a century in any condition and on any wicket in the world. I just want to give the team that kind of a start. It will be nice to get another hundred,” Gayle said. “However it also depends on the conditions as well and how the wicket is playing,” he said. Asked about the tremendous pressure on him to perform every time, when he goes out to bat, the Jamaican dasher said it indeed was a challenge to live up to the expectations. “It creates a lot of pressure as expectations are rising. When you actually set a trend, then people expect you to come good at all times. You have fans worldwide who want me to do well. That’s what they pay for and want to see. But it’s not going to happen all the time but when I do get a chance I try to entertain people as much as possible,” he said. “We are here to retain the title and that’s not going to be easy but we are ready for it and we are ready for the challenges. Our first priority is to make it to the last four, it’s a tough group. Everybody is looking to win the tournament.”";            

              String[] sentences = sentenceDetector.sentDetect(articleText); // -----D

                    

                     int index = 0;

                     for (int i = 0; i < sentences.length; i++) {

                           index++;

                           String sentence = sentences[i];

                           System.out.println("Sentence : " + index  + " " + sentence); // --- printing seach sentence.

                          

                     }

                    

              } catch (Exception e) {

                     System.out.println("Exception : " + e);

                    

              }

       }

}

Output:

Sentence : 1 Chris Gayle on Monday sounded out a warning to the rival teams ahead of the World Twenty20 by declaring that he can score a hundred irrespective of the conditions.

Sentence : 2 “I am capable of scoring a century in any condition and on any wicket in the world.

Sentence : 3 I just want to give the team that kind of a start.

Sentence : 4 It will be nice to get another hundred,” Gayle said.

Sentence : 5 “However it also depends on the conditions as well and how the wicket is playing,” he said.

Sentence : 6 Asked about the tremendous pressure on him to perform every time, when he goes out to bat, the Jamaican dasher said it indeed was a challenge to live up to the expectations.

Sentence : 7 “It creates a lot of pressure as expectations are rising.

Sentence : 8 When you actually set a trend, then people expect you to come good at all times.

Sentence : 9 You have fans worldwide who want me to do well.

Sentence : 10 That’s what they pay for and want to see.

Sentence : 11 But it’s not going to happen all the time but when I do get a chance I try to entertain people as much as possible,” he said.

Sentence : 12 “We are here to retain the title and that’s not going to be easy but we are ready for it and we are ready for the challenges.

Sentence : 13 Our first priority is to make it to the last four, it’s a tough group.

Sentence : 14 Everybody is looking to win the tournament.”

-----------------------------------------------------------------------------

Similarly the following code, tokenizes the words from the same article:

InputStream modelIn = new FileInputStream(
"src/main/resources/models/en-token.bin");
TokenizerModel tModel = new TokenizerModel(modelIn);

TokenizerME tokenizer = new TokenizerME(tModel);

String articleText = "Chris Gayle on Monday sounded out a warning to the rival teams ahead of the World Twenty20 by declaring that he can score a hundred irrespective of the conditions. “I am capable of scoring a century in any condition and on any wicket in the world. I just want to give the team that kind of a start. It will be nice to get another hundred,” Gayle said. “However it also depends on the conditions as well and how the wicket is playing,” he said. Asked about the tremendous pressure on him to perform every time, when he goes out to bat, the Jamaican dasher said it indeed was a challenge to live up to the expectations. “It creates a lot of pressure as expectations are rising. When you actually set a trend, then people expect you to come good at all times. You have fans worldwide who want me to do well. That’s what they pay for and want to see. But it’s not going to happen all the time but when I do get a chance I try to entertain people as much as possible,” he said. “We are here to retain the title and that’s not going to be easy but we are ready for it and we are ready for the challenges. Our first priority is to make it to the last four, it’s a tough group. Everybody is looking to win the tournament.”";
String[] tokens = tokenizer.tokenize(articleText);

int index = 0;
String tokenString = "";
for (int i = 0; i < tokens.length; i++) {
index++;
tokenString = tokenString + tokens[i] + "|";
}
System.out.println("No. of tokens : " + tokenString.length());
System.out.println(tokenString);

Output:
No. of tokens : 1244
Chris|Gayle|on|Monday|sounded|out|a|warning|to|the|rival|teams|ahead|of|the|World|Twenty20|by|declaring|that|he|can|score|a|hundred|irrespective|of|the|conditions|.|“|I|am|capable|of|scoring|a|century|in|any|condition|and|on|any|wicket|in|the|world|.|I|just|want|to|give|the|team|that|kind|of|a|start|.|It|will|be|nice|to|get|another|hundred|,|”|Gayle|said|.|“However|it|also|depends|on|the|conditions|as|well|and|how|the|wicket|is|playing|,|”|he|said|.|Asked|about|the|tremendous|pressure|on|him|to|perform|every|time|,|when|he|goes|out|to|bat|,|the|Jamaican|dasher|said|it|indeed|was|a|challenge|to|live|up|to|the|expectations|.|“It|creates|a|lot|of|pressure|as|expectations|are|rising|.|When|you|actually|set|a|trend|,|then|people|expect|you|to|come|good|at|all|times|.|You|have|fans|worldwide|who|want|me|to|do|well|.|That’s|what|they|pay|for|and|want|to|see|.|But|it|’s|not|going|to|happen|all|the|time|but|when|I|do|get|a|chance|I|try|to|entertain|people|as|much|as|possible|,|”|he|said|.|“We|are|here|to|retain|the|title|and|that|’s|not|going|to|be|easy|but|we|are|ready|for|it|and|we|are|ready|for|the|challenges|.|Our|first|priority|is|to|make|it|to|the|last|four|,|it|’s|a|tough|group|.|Everybody|is|looking|to|win|the|tournament|.|”|

Spring Annotation based configuration - reading from property file

Spring can be configured using context xml files or using java annotations.

@Configuration can be used if you want to configure using java.

Full configuration code:

@Configuration

@EnableWebMvc

@ComponentScan(basePackages = "com.cv")

@EnableMongoRepositories(basePackages = { "com.cv.framework.mongorepositories",

              "com.cv.app.repository" })

@PropertySource(value = "classpath:app.properties")

public class AppConfig extends WebMvcConfigurerAdapter

       @Inject

       Environment environment;

       @Bean

       public InternalResourceViewResolver configureInternalResourceViewResolver() {

              InternalResourceViewResolver resolver = new InternalResourceViewResolver();

              resolver.setPrefix("/WEB-INF/views/");

              resolver.setSuffix(".jsp");

              return resolver;

       }

       @SuppressWarnings("deprecation")

       @Bean

       public Mongo mongo() throws Exception {

              return new Mongo(environment.getProperty("ip"));

       }

       @Bean

       public MongoTemplate mongoTemplate() throws Exception {

              return new MongoTemplate(mongo(),

                           environment.getProperty("mdbname"));

       }

}

@Configuration tells that the current java file is a spring configuration file. 

@ComponentScan tells the container to scan all the java files that starts with the package com.cv

@EnableMongoRepository informs the container where to search for mongo Repositories. 

@PropertySource annotation defines the property file this annotation java file uses to pull configurable values for the application. 

Environment is a spring api class which is used to read from the properties file. 

environment.getProperty("mdbname") tries to read the property mdbname from the app.properties file. 

Java based spring configuration is easier than the xml configuration since it throws all the errors at compile time and the context sensitive help comes very handy. 

Some developers prefer to keep some configuration in the xml to locate easily. 

Spring security using Java configuration

Authentication can be done in 2 ways in spring - using context xml files or using the latest java based configuration. This article explains how to implement spring security using java configurations.

The below steps need to be followed in order to configure security in spring applications.

• Define spring security security filter chain.
• Create custom user details service
• Security configuration

1Define spring security security filter chain.

       public class WebAppInitializer implements WebApplicationInitializer {

              public void onStartup(ServletContext servletContext)

                     throws ServletException {

              .

              .

              .

             

              servletContext.addFilter("springSecurityFilterChain",

                           new DelegatingFilterProxy("springSecurityFilterChain"))

                     .addMappingForUrlPatterns(EnumSet.allOf(DispatcherType.class),

                                         true, "/*");

              .

              .

              .

              }

       }

TThe above approach eliminates the need for using a web.xml. The springsecurityfilterchain is defined in this java

fifile instead of web.xml.

Create custom user details service class.

       @Service

       public class AppUserDetailsService implements UserDetailsService {

              @Autowired

              private AppUserRepository appUserRepository;

              @Override

              @Transactional

              public UserDetails loadUserByUsername(String userId)

                     throws UsernameNotFoundException {

                     UserValue userValue = null;

                     List<GrantedAuthority> grantedAuthorities = new  ArrayList                               <GrantedAuthority>();

                     AppUser appUser = null;

                     appUser = appUserRepository.findByUserId(userId);

                     if (appUser != null) {

                            grantedAuthorities.add(new SimpleGrantedAuthority(appUser

                                  .getAppRole().getName()));

                            userValue = new UserValue(

                                  appUser.getId(), appUser. getUserId(),

                                  appUser.getPassword(), grantedAuthorities,

                                   appUser.getFirstName(), appUser.getLastName());

                     }

                     return userValue;

              }

       }

 There are different ways to configure security, this approach uses a custom User details service which loads the user and role information from the db and returns it to the framework, the framework then stores the user and role information in the session for further processing

1Create security configuration java class

@Configuration

@EnableWebSecurity

@EnableGlobalMethodSecurity(prePostEnabled = true)

public class SecurityConfig extends WebSecurityConfigurerAdapter {

       @Autowired

       AppUserDetailsService appUserDetailsService;

       @Autowired

       public void configureGlobal(AuthenticationManagerBuilder auth)

                     throws Exception {

              auth.userDetailsService(appUserDetailsService);

       }

       @Override

       public void configure(WebSecurity builder) throws Exception {

              builder.expressionHandler(webexpressionHandler()).ignoring()

                           .antMatchers("/resources/**");

       }

       @Bean(name = "webexpressionHandler")

       public DefaultWebSecurityExpressionHandler webexpressionHandler() {

              return new DefaultWebSecurityExpressionHandler();

       }

       @Override

       protected void configure(HttpSecurity http) throws Exception {

              http.csrf().disable().authorizeRequests().

                                  .antMatchers("/loginPage").permitAll().

                                  anyRequest().fullyAuthenticated().and()                                                   .formLogin().loginPage("/loginPage").

                                  loginProcessingUrl("/j_spring_security_check")

                                  .usernameParameter("j_username")

                                   .passwordParameter("j_password").

                                  failureUrl("/errorPage")

                                   .defaultSuccessUrl("/myhome").permitAll().and().

                                  logout().logoutUrl("/j_spring_security_logout")

                     .logoutSuccessUrl("/loginPAge").deleteCookies("JSESSIONID")

                           .invalidateHttpSession(true);

       }

}

The configure method can be used to define the loginpage, logout page, the success url, failure url and whether to delete cookies and invalidate session while logout. 

• The configure method which accepts WebSecurity can be used to tell the resource folders so that those can be ignored by the security frameworks.
•  Now all the urls except the one in the resources folder will be intercepted by the security framework and will be redirected to the login page
•  Once the user enters the user id and password, the AppUserDetailsService.loadUserByUsername will be called by passing the current login userid. This method loads user information and passes it to the security framework
•  The framework then validates the credentials and if it is successful, then displays the home page based on the configuration defined in the security config class.
•  When the user logs out, the session is invalidated and the controls goes back to the login page.