Saturday, 21 June 2014

[Solution] .bat file don't proceed after mvn clean install

Executing .bat does not proceed after mvn clean install.

mvn -o clean install
echo $classpath  -- This never executes

Solution :

call mvn -o clean install 
echo $classpath  

Reason: .bat file, halts after calling another program.  CALL command is invoke another program from the current and proceed further

Reference: http://www.computerhope.com/call.htm

Saturday, 5 April 2014

Spring : context:component-scan vs context:annotation-config

Whats the difference between component-scan and annotation-config

  • <context:annotation-config/>  -   Looks for @Autowired and JSR annotation, It does not identify the @component, @configuration annotations.  It just autowires existing beans
  • whereas <context:component-scan  base-package="org.first" />  Does recoginize @Autowired, @component and other annotations also.
  • <context:component-scan> also does  <context:annotation-config/>  and also scans packages to find registeredbeans

Example  1 :  Let's define the classes in beans.xml and also annotate with @Component and @Autowired

package org.first;
@Component
public class FirstServiceImpl implements FirstService{
    public Name userName;

    public FirstServiceImpl(){
        System.out.println("new FirstServiceImpl()");
    }

    @Autowired
    public void setUserName(final Name userName){
        System.out.println("setUserName(final Name userName)");
        this.userName = userName;
    }
//getters, setters, other constructors
}

package org.first;
@Component
public class Name{
    String name = "new";

    public Name(){
        super();
        System.out.println("new Name()");
    }
   //getters, setters, other constructors
}

beans.xml

<beans><!-- Add Namesapece here -->
    <bean name="userName" class="org.first.Name">
        <property name="name" value="Vidhya"></property>
    </bean>

    <bean name="firstService" class="org.first.FirstServiceImpl">
        <property name="userName" ref="userName"></property>
    </bean>
</beans>


OUTPUT : This will instantiate the userName and firstService classes, because both classes are defined in the xml

new Name()
new FirstServiceImpl()
setUserName(final Name userName)



Example  2 :  Lets try to use <context-annotation-config> :  


package org.first;
@Component
public class FirstServiceImpl implements FirstService{
    public Name userName;
    public FirstServiceImpl(){
        System.out.println("new FirstServiceImpl()");
    }

    @Autowired
    public void setUserName(final Name userName){
        System.out.println("setUserName(final Name userName)");
        this.userName = userName;
    }
//getters, setters, other constructors
}

package org.first;
public class Name{
    String name = "new";

    public Name(){
        super();
        System.out.println("new Name()");
    }
   //getters, setters, other constructors
}
beans.xml
 <beans><!-- Add Namesapece here -->
    <context:annotation-config/>
</beans>

OUTPUT : This will NOT do anything. NO OUTPUT. Why? The annotation-config cannot know about the beans unless defined. 

How to fix this? We need to add bean definitions. Lets add the bean definitions in the beans.xml



Example  3 :  Lets use <context-annotation-config> and bring back the bean definitions.


beans.xml
 <beans><!-- Add Namesapece here -->
    <context:annotation-config/>

    <bean name="userName" class="org.first.Name">
        <property name="name" value="Vidhya"></property>
    </bean>

    <bean name="firstService" class="org.first.FirstServiceImpl">
        <property name="userName" ref="userName"></property>
    </bean>
</beans>

OUTPUT : This will instantiate the userName and firstService classes, because both classes are defined in the xml

new Name()
new FirstServiceImpl()
setUserName(final Name userName)

Example  4 :  So, what's the use of annotation-config? We saw that annotation-config cannot load @component, Now lets see if it can autowire, with same class as in Example 2.


beans.xml
 <beans><!-- Add Namesapece here -->
    <context:annotation-config/>

    <bean name="userName" class="org.first.Name">
        <property name="name" value="Vidhya"></property>
    </bean>

    <bean name="firstService" class="org.first.FirstServiceImpl">
        <property name="userName" ref="userName"></property>
    </bean>
</beans>


OUTPUT : 

new Name() new FirstServiceImpl() setUserName(final Name userName)
Looks like annotation-config can autowire, but cannot instantiate @Component


Example  5 :  Lets use <context:component-scan> now. As per definition, it can read all@component classes and also autowire. We will check that

package org.first;
@Component
public class FirstServiceImpl implements FirstService{
    public Name userName;

    public FirstServiceImpl(){
        System.out.println("new FirstServiceImpl()");
    }

    @Autowired
    public void setUserName(final Name userName){
        System.out.println("setUserName(final Name userName)");
        this.userName = userName;
    }
//getters, setters, other constructors
}

package org.first;
@Component
public class Name{
    String name = "new";

    public Name(){
        super();
        System.out.println("new Name()");
    }
   //getters, setters, other constructors
}
beans.xml
 <beans><!-- Add Namespace here -->
     <context:component-scan base-package="org.first" />
</beans>

OUTPUT : There you go.. Now we achieve with single line in beans.xml, which all @Component and @Autowired annotations.
new FirstServiceImpl()
new Name()
setUserName(final Name userName)

SUMMARY:

1. <context:component-scan> is one stop solution for @Autowired and @Component 
2.<context:annotation-config> can only do @Autowired.
3. I am readying the annotation-config is very useful in the web context with DispatcherServlet. But need to try that. Probably will write about it later when I try it.

References

http://docs.spring.io/spring/docs/3.0.0.M3/reference/html/ch04s11.html
http://www.tutorialspoint.com/spring/spring_annotation_based_configuration.htm
http://stackoverflow.com/questions/7414794/difference-between-contextannotation-config-vs-contextcomponent-scan

Example: Spring configuration using AnnotationConfigApplicationContext without XML


Below is the example for Bean configuration using AnnotationConfigApplicationContext.

AnnotationConfigApplicationContext(<Package to scan>) or
AnnotationConfigApplicationContext(@Configuration class with @bean declaration)

We have to make sure that the same beans are not marked @component and also defined in @configuration class



Class with @component annotation

package org.first;

import org.springframework.stereotype.Component;

@Component
public class FirstServiceImpl implements FirstService
{

    public FirstServiceImpl()
    {
    }

    public String printMessage()
    {
        final String s = "--printMessage()---";
        System.out.println(s);
        return s;

    }

    public String messagePrint()
    {
        final String s = "--messagePrint()---";
        System.out.println(s);
        return s;

    }

    public FirstServiceImpl getfirstService()
    {
        return new FirstServiceImpl();
    }
}


Test code


import org.first.FirstService;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class AOPTest
{

    ApplicationContext ctx = new AnnotationConfigApplicationContext("org.first");

    @Test
    public void testContext()
    {
        final FirstService service = ctx.getBean(FirstService.class);
        service.printMessage();

    }
}

Example : Spring context:component-scan and @Component

Automatic Component scanning is useful in defining beans and autowiring them without defining them in an .xml file


Below is the example  with xml and  and beans annotated

beans.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:aop="http://www.springframework.org/schema/aop" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans 
        http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
        http://www.springframework.org/schema/aop
        http://www.springframework.org/schema/aop/spring-aop-3.0.xsd 
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context-3.0.xsd">

    <context:component-scan  base-package="org.first" />
</beans>


Class with @component annotation

package org.first;

import org.springframework.stereotype.Component;

@Component
public class FirstServiceImpl implements FirstService
{

    public FirstServiceImpl()
    {
    }

    public String printMessage()
    {
        final String s = "--printMessage()---";
        System.out.println(s);
        return s;

    }

    public String messagePrint()
    {
        final String s = "--messagePrint()---";
        System.out.println(s);
        return s;

    }

    public FirstServiceImpl getfirstService()
    {
        return new FirstServiceImpl();
    }
}


Test code


import org.first.FirstService;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class AOPTest
{

    ApplicationContext ctx = new ClassPathXmlApplicationContext("beans.xml");

    @Test
    public void testContext()
    {
        final FirstService service = ctx.getBean(FirstService.class);
        service.printMessage();

    }
}

Friday, 4 April 2014

Spring Controller with Hibernate using ContextLoaderListener

  • Below is a simple example to show how to instantiate the spring context in ContextLoaderListener and use in a HTTPServlet.
  • There are other ways of directly using Dispatcher servlet, but the is the basic way for a beginner.
  • Eclipse project for this example can be found here: spring-web-contextloader.zip
     
  • The given codebase does not contain the database scripts. You may want to create ur own tables and change the hibernate.cfg.xml and beans.xml with the database connection details
  • This code has been tested in a jetty webserver. But should work in any webserver





Web.xml -

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">

    <!-- Spring app context using a listener  -->
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>

    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>/WEB-INF/beans.xml</param-value>
    </context-param>



    <display-name>spring-web</display-name>
    <welcome-file-list>
        <welcome-file>index.jsp</welcome-file>
    </welcome-file-list>

    <!-- Trying the simple Servlet type -->
    <servlet>
        <description></description>
        <display-name>EmployeeServlet</display-name>
        <servlet-name>EmployeeServlet</servlet-name>
        <servlet-class>org.controllers.EmployeeServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>EmployeeServlet</servlet-name>
        <url-pattern>*.action</url-pattern>
    </servlet-mapping>

</web-app> 

beans.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:context="http://www.springframework.org/schema/context"
    xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans 
              http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
              http://www.springframework.org/schema/context
              http://www.springframework.org/schema/context/spring-context-3.0.xsd
              http://www.springframework.org/schema/mvc 
              http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd">

    <bean name="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <property name="driverClassName" value="org.hsqldb.jdbc.JDBCDriver" />
        <property name="url" value="jdbc:hsqldb:hsql://localhost/section1" />
        <property name="username" value="sa" />
        <property name="password" value="" />
    </bean>

    <bean name="sessionFactory" class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
        <property name="dataSource" ref="dataSource"></property>
        <property name="packagesToScan" value="org.entity" />
        <property name="configLocation" value="classpath:hibernate.cfg.xml" />
    </bean>


    <bean name="employeeDAO" class="org.dao.EmployeeDAO">
        <property name="sessionFactory" ref="sessionFactory" />
    </bean>

</beans>


hibernate.cfg.xml

<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>
    <session-factory>
        <property name="hibernate.connection.driver_class">org.hsqldb.jdbc.JDBCDriver</property>
        <property name="hibernate.connection.url">jdbc:hsqldb:hsql://localhost/section1</property>
        <property name="hibernate.connection.username">sa</property>
        <property name="hibernate.connection.password"></property>
        <property name="hibernate.hbm2ddl.auto">update</property>

        <!-- property name="hibernate.connection.pool_size">1</property -->
        <property name="hibernate.show_sql">true</property>
        <property name="hibernate.format_sql">true</property>
        <property name="hibernate.dialect">org.hibernate.dialect.HSQLDialect</property>


        <!-- mapping class="org.entity.Product" / -->
        <mapping class="org.entity.Employee" />
    </session-factory>
</hibernate-configuration>


Servlet - Manual Controller

package org.controllers;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.dao.EmployeeDAO;
import org.entity.Employee;
import org.springframework.context.ApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;

public class EmployeeServlet extends HttpServlet
{
    ApplicationContext ctx = null;

    @Override
    protected void service(final HttpServletRequest req, final HttpServletResponse resp)
            throws ServletException, IOException
    {
        if (ctx == null)
        {
            ctx = WebApplicationContextUtils.getWebApplicationContext(getServletContext());
        }
        final String uri = req.getRequestURI();
        System.out.println("---------------" + uri);
        if (uri.contains("employee.action"))
        {
            getEmployee(req, resp);
        }

    }

    public void getEmployee(final HttpServletRequest req, final HttpServletResponse resp)
            throws ServletException, IOException
    {
        try
        {
            final EmployeeDAO dao = ctx.getBean("employeeDAO", EmployeeDAO.class);
            final Employee emp = dao.getEmployee(null);
            req.setAttribute("emp", emp);
            req.getRequestDispatcher("employee.jsp").forward(req, resp);
        }
        catch (final Exception e)
        {
            e.printStackTrace();
        }

        req.getRequestDispatcher("errors.jsp").forward(req, resp);
    }
}


DAO

package org.dao;

import org.entity.Employee;
import org.hibernate.SessionFactory;

public class EmployeeDAO
{

    private SessionFactory sessionFactory;

    public void setSessionFactory(final SessionFactory sessionFactory)
    {
        this.sessionFactory = sessionFactory;
    }

    public Employee getEmployee(Integer id)
            throws Exception
    {
        try
        {

            if (id == null)
            {
                id = 1;
            }
            final Employee emp = (Employee) sessionFactory.openSession().get(Employee.class, id);
            System.out.println("--sessionFactory.get(Employee.class, " + id + ")   ---> " + emp);
            return emp;

        }
        catch (final Exception e)
        {
            e.printStackTrace();
            throw e;
        }
    }
}


Entity

package org.entity;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

@Entity
public class Employee {
 @Id
 @GeneratedValue(strategy = GenerationType.IDENTITY)
 private Integer employeeId;
 private String firstName;
 private String lastName;
 private String jobTitle;
 private Double salary;

 public Employee() {
 }

 public Employee(Integer employeeId, String firstName, String lastName,
   String jobTitle, Double salary) {
  this.employeeId = employeeId;
  this.firstName = firstName;
  this.lastName = lastName;
  this.jobTitle = jobTitle;
  this.salary = salary;
 }
.....................
Please pick up the code from the zip file
}
 

employee.jsp

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
Employee : <%=request.getAttribute("emp") %>
<br/>
Employee using taglig : <c:out value="${requestScope.emp}"></c:out>
</body>
</html>

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>spring-web</groupId>
    <artifactId>spring-web</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>war</packaging>
    <properties>
        <!-- Spring -->
        <spring-framework.version>3.2.3.RELEASE</spring-framework.version>

        <!-- Hibernate / JPA -->
        <hibernate.version>4.2.1.Final</hibernate.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>3.2.0.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>3.2.0.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-orm</artifactId>
            <version>3.2.0.RELEASE</version>
        </dependency>
        <!-- Hibernate -->
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-entitymanager</artifactId>
            <version>${hibernate.version}</version>
        </dependency>
        <!-- db -->
        <dependency>
            <groupId>org.hsqldb</groupId>
            <artifactId>hsqldb</artifactId>
            <version>2.2.8</version>
        </dependency>

    </dependencies>
    <build>
        ....................
        <!-- Please see attached zip containing the code --> 
    </build>
</project>
 
OUTPUT
 
 

Thursday, 3 April 2014

Elasticsearch shards and replicas

Shards and replicas : Here is a good explanation on this topic http://stackoverflow.com/a/15705989


Routing  clustering and index internals: http://exploringelasticsearch.com/advanced_techniques.html#ch-advanced


Cluster join example : http://thediscoblog.com/blog/2013/09/03/effortless-elasticsearch-clustering/