SpEL : The power full tool of Spring 3.0

2011-09-28T20:13:00.000-07:00

SpEL: Spring Expression Language

What a power full tool it is.
it can do below things.
Suppose you have Two classes Department and Employee
and department having list property of Employee
So to copy list of one department to other you can do like:

<bean id="finance" class="xyz.Deparment"/>
<property name=""empList" value="#{otherDep.empList}"/>
</bean>
it is something like
Department finance = new Department();
finance.setEmpList(otherDep.getEmpList);

===========================
Even String operations are easily performed using SpEL
Like you are getting songs with
<property name="song"value="#{songSelector.selectSong()}"/>

now if you want to get Song in upper case you can do the below.
<propertyname="song"value="#{songSelector.selectSong().toUpperCase()}"/>

or you can also check null before doing String operations.to avoid NPE
<propertyname="song"value="#{songSelector.selectSong()?.toUpperCase()}"/>.
========================================================
to call the static methods you can use
T()
like you want to use random method of Math class you can do following.
<propertyname="randomNumber"value="#{T(java.lang.Math).random()}"/>
===============================================
You can perform Arithmetic operations.
<propertyname="result"value="#{2 + T(java.lang.Math).random()* abc.total}"/>
====================================
Also Logical, Conditional and Logical Operator can be used by using SpEL

Now come the most powerful feature of SpEL (Collections)
you directly access any element of a collection.

<property name="employee" value="#{empList[2]}"/>
can get a sub set of collection like employes having age > 25
<property name="youngerEmpList"value="#{empList.?[age gt 25]}"/>
.^[] and .$[], for selecting the first and last matching items (respectively)
<property name="youngerEmpList"value="#{empList.^[age gt 25]}"/>
<property name="youngerEmpList"value="#{empList.$[age gt 25]}"/>
you can access Environment variables
<propertyname="javahome"value="#{systemEnvironment['JAVA_HOME']}"/>
system properties
<propertyname="mvnversion"value="#{systemProperties['mevan.version']}"/>

PROJECTING COLLECTIONS
you can directly get the property list from a object like
like you have a City object with property name, state, street.
to get the names of all the cities you can do
<propertyname="cityNames"value="#{cities.![name]}"/>
or to do more
<propertyname="cityNames"value="#{cities.![name+','+state]}"/>
and to do more than more
<propertyname="cityNames" value="#{cities.?[populationgt100000].![name+','+state]}"/>

Thanks
Amit Kathpal

Bean Scoping in Spring Tech

2011-09-27T23:43:00.000-07:00

By Default the Beans in Spring Frame Work are singleton.

It is beneficial some time but there may be cases where you need your own copy of bean.

To get your own copy for every bean you can use scope attribute. Like. scope="prototype"

There are five type of scopes available in Spring

singleton Scopes the bean definition to a single instance per Spring container (default).

Prototype Allows a bean to be instantiated any number of times (once per use).

request Scopes a bean definition to an HTTP request. Only valid when used with a web-capable Spring context (such as with Spring MVC).

session Scopes a bean definition to an HTTP session. Only valid when used with a web-capable Spring context (such as with Spring MVC).

global-session Scopes a bean definition to a global HTTP session. Only valid when used in a portlet context.

Thanks

Amit Kathpal

Spring Technology

SpEL : The power full tool of Spring 3.0

Bean Scoping in Spring Tech