org.springframework.beans.factory.BeanDefinitionStoreException: Unexpected exception parsing XML document from ServletContext resource

Exception :-

org.springframework.beans.factory.BeanDefinitionStoreException: Unexpected exception parsing XML document from ServletContext resource [/WEB-INF/demo-servlet.xml]; nested exception is java.lang.NoClassDefFoundError: org/aopalliance/intercept/MethodInterceptor
    at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.doLoadBeanDefinitions(XmlBeanDefinitionReader.java:412)
    at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:334)
    at org.springframework.beans.factory.xml.XmlBeanDefinitionReade

First ensure that you have included aopalliance jar in classpath. Click here to download aopalliance-1.0.jar 

If you are using maven then add following dependency in pom.xml
 

<dependency>
    <groupId>aopalliance</groupId>
    <artifactId>aopalliance</artifactId>
    <version>1.0</version>
</dependency>

Two Datasource in Spring/Hiberate

We can create two datasource in a single spring/hibernate application.

There are following steps required to implement this:-

Create JNDI Datasource while using Tomcat :- 

1. Resource entry in server.xml under <GlobalNamingResources> for both datasources
   You can find server.xml in following path in Tomcat folder :-
    c://Tomcat/conf/server.xml

<globalnamingresources>
    <resource name="jdbc/first"  driverclassname="com.microsoft.sqlserver.jdbc.SQLServerDriver" maxwait="5000" password="makecodeeasy" type="javax.sql.DataSource" url="jdbc:sqlserver://localhost:1433;DatabaseName=DataTest" username="makecodeeasy" validationquery="select 1">
    </resource>

 <resource name="jdbc/second"  driverclassname="com.microsoft.sqlserver.jdbc.SQLServerDriver" maxwait="5000" password="123" type="javax.sql.DataSource" url="jdbc:sqlserver://192.182.21.66:1433;DatabaseName=Second" username="sa" validationquery="select 1">
    </resource>
 </globalnamingresources>

Note :- Database used here in MS Sql server 2008. You can use any database. You need to change driverClassname, url, username and password according to  database.
2. Do the entry in web.xml for both resources
   You can find web.xml in WEB-INF folder of your application

<resource-ref>
  <description>DB Connection Pooling</description> 
  <res-ref-name>java:comp/env/jdbc/first</res-ref-name> 
  <res-type>javax.sql.DataSource</res-type> 
  <res-auth>Container</res-auth> 
  <res-sharing-scope>Shareable</res-sharing-scope> 
</resource-ref>


<resource-ref>
  <description>DB Connection Pooling</description> 
  <res-ref-name>java:comp/env/jdbc/second</res-ref-name> 
  <res-type>javax.sql.DataSource</res-type> 
  <res-auth>Container</res-auth> 
  <res-sharing-scope>Shareable</res-sharing-scope> 
</resource-ref>

3. Use datasource in applicationContext or spring context file

<bean id="firstDataSource" class="org.springframework.jndi.JndiObjectFactoryBean">
  <property name="jndiName" value="java:comp/env/jdbc/first" /> 
  <property name="resourceRef" value="true" /> 
</bean>

<bean id="secondDataSource" class="org.springframework.jndi.JndiObjectFactoryBean">
  <property name="jndiName" value="java:comp/env/jdbc/second" /> 
  <property name="resourceRef" value="true" /> 
</bean> 

4. Create two session factory for using two datasource.
   

   <bean id="firstSessionFactory" class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean" p:dataSource-ref="firstDataSource" p:configLocation="${hib.config}" p:packagesToScan="com.org.xyz.domain">
   </bean>

   <bean id="secondSessionFactory" class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean" p:dataSource-ref="secondDataSource" p:configLocation="${hib.config}" p:packagesToScan="com.org.abc.domain">
   </bean>

   
   
5. Now these session factories can be used in Hibernate application.
   

JNDI Datasource in spring

There are two sources of database connections - either a  DataSource or a  DriverManager.

JNDI
The Java Naming and Directory Interface (JNDI) is part of the Java platform, providing applications based on Java technology with a unified interface to multiple naming and directory services. You can build powerful and portable directory-enabled applications using this industry standard.

Create JNDI Datasource while using Tomcat :- 

1. Resource entry in server.xml under <GlobalNamingResources>
   You can find server.xml in following path in Tomcat folder :-
    c://Tomcat/conf/server.xml

<globalnamingresources>
    <resource name="jdbc/test"  driverclassname="com.microsoft.sqlserver.jdbc.SQLServerDriver" maxwait="5000" password="makecodeeasy" type="javax.sql.DataSource" url="jdbc:sqlserver://localhost:1433;DatabaseName=DataTest" username="makecodeeasy" validationquery="select 1">
    </resource>
</globalnamingresources>

Note :- Database used here in MS Sql server 2008. You can use any database. You need to change driverClassname, url, username and password according to  database.
2. Do the entry in web.xml
   You can find web.xml in WEB-INF folder of your application

<resource-ref>
  <description>DB Connection Pooling</description> 
  <res-ref-name>java:comp/env/jdbc/test</res-ref-name> 
  <res-type>javax.sql.DataSource</res-type> 
  <res-auth>Container</res-auth> 
  <res-sharing-scope>Shareable</res-sharing-scope> 
</resource-ref>

3. Use datasource in applicationContext or spring context file

<bean id="dataSource" class="org.springframework.jndi.JndiObjectFactoryBean">
  <property name="jndiName" value="java:comp/env/jdbc/test" /> 
  <property name="resourceRef" value="true" /> 
</bean>

4. Your Datasource is ready to use. It can also be used in hibernate.
   

Logger in Spring web application

The logging API is designed to let a Java program, servlet, applet, EJB, etc. produce messages of interest to end users, system administrators, field engineers, and software developers. Especially in production situations, where things can't be run in a debugger, or if doing so masks the problem that is occurring (because it is timing related, for example), such logs are frequently the greatest (and sometimes the only) source of information about a running program.

Step by Step implementing Logger in Spring Web Application:-

1. Download log4j jar and put to application build path / put to WEB-INF lib folder.
   Download JAR link
2. Create a file name Log4js.properties

log4j.rootCategory=INFO,S,rollingFile

log4j.appender.S =org.apache.log4j.ConsoleAppender
log4j.appender.S.layout =org.apache.log4j.PatternLayout
log4j.appender.S.layout.ConversionPattern = %d{yyyy-MM-dd HH:mm:ss} %c{1} [%p] %m%n
log4j.appender.rollingFile = org.apache.log4j.DailyRollingFileAppender

#provide path to your location where you want logs created. For now its logs folder of tomcat.
log4j.appender.rollingFile.File = ${catalina.home}/logs/loggerDemo.log
log4j.appender.rollingFile.Append = true
log4j.appender.rollingFile.Threshold = ALL
log4j.appender.rollingFile.DatePattern = '.'yyy-MM-dd
log4j.appender.rollingFile.layout = org.apache.log4j.PatternLayout
log4j.appender.rollingFile.layout.ConversionPattern = %d{yyyy-MM-dd HH:mm:ss} %c{1} [%p] %m%n

Here ${catalina.home} :- The Tomcat Web container uses a file system directory, called the catalina home directory, to hold files that are common to the entire container.
You can also give other path for generating log file.

3. Entry in web.xml file

 
      log4jConfigLocation
      /WEB-INF/resources/log4j.properties
    

     
        org.springframework.web.util.Log4jConfigListener
    

4. JAVA Code for logger.

import org.apache.log4j.Logger;
public class LoggerController {

	private static final Logger LOGGER = Logger.getLogger(LoggerDemo.class);

	@RequestMapping(method=RequestMethod.GET, value="/login/{id}")
	@ResponseBody public void getUserName(@PathVariable String id) {
		LOGGER.info("Calling service User authentication" + id);
	}

}

5. Enjoy :)

Spring Expression Language (SpEL)

SpEL

SpEL is an Expression Language that wire the values into beans properties using expression at runtime.

Features

• Literal expressions :-
  Integer Number :-
  <property name="num" value="#{5}">  The #{} markers are a clue to Spring that the content that they contain is a SpEL expression.
  
  Floating-point numbers :-
  <property name="num" value="#{50.5}"/>
  
  Scientific notation :-
  <property name="num" value="#{2e5}"/>
  
  String :-
  <property name='str' value='#{"laptop"}'/>
• Boolean :- 
  <property name="val" value="#{true}"/>
  <property name="val" value="#{false}"/>
• Referencing Beans :-
  <property name="name" value="#{Employee}"/>
  This is same as :-
  <property name="name" ref="Employee"/>
  
  Referring another bean property :-
  <bean id="cars" class="com.proj.vehicleApp.Cars"> 
       <property name="speed" value="#{bike.speed}" />
  </bean>
  Call Method :-
  <bean id="cars" class="com.proj.vehicleApp.Cars">   
      <property name="speed" value="#{bike.getSpeed()}" /></bean>
• Arithmetic   +, -, *, /, %, ^
• Relational   <, >, ==, <=, >=, lt, gt, eq, le, ge
• Logical and, or, not, |
• Conditional ?: (ternary), ?: (Elvis)
• Regular expression matches

MVC

MVC = Model-View-Controller
 Clearly separates business, navigation and presentation logic.

• Controller :- Handles navigation logic and interacts with the service tier for business logic.
• Models :- Models represent knowledge. A model could be a single object (rather uninteresting), or it could be some structure of objects.
• View :- A view is a (visual) representation of its model. It would ordinarily highlight certain attributes of the model and suppress others. It is thus acting as a presentation filter.