Spring Bean config/ Dependency Injection

XML

BeanFactory/ApplicationContext

1. XmlBeanFactory
2. ClassPathXmlApplicationContext
3. XmlWebApplicationContext

Lazy mode

Spring default is not lazy mode, when spring starts up, it inits all beans.

If we want bean to init when calling ac.getBean()
do this:
<beans .... default-lazy-init="true">


Bean Scope

<bean scope="singleton">

singleton: return the same instance when getBean(default)
prototype: create new instance everytime when getBean
request: HTTP request life cycle
session: HTTP Session life cycle
global session: Global HTTP Session life cycle, spring portlet context

Try best to avoid scope "prototype", which is heavy memory usage and mostly unnecessary

Set property with another bean

Use <ref>

<property name="emp">
 <ref bean="beanId" />
</property>

Property Injection with Collections/Array

map
set
list
collection
int[]

Array/List/Set values are primitive types

<bean id="department" class="com.gvace.collection.Department">
 <property name="name" value="Business"></property>
 <property name="empName">
  <list>
   <value>aaa</value>
   <value>bbb</value>
   <value>ccc</value>
  </list>
 </property>
</bean>

Array/List/Set values are objects
Use ref to link the instance of other beans

<bean id="department" class="com.gvace.collection.Department">
 <property name="name" value="Business"></property>
 <property name="employee">
  <set>
   <ref bean="emp1"/>
   <ref bean="emp2"/>
  </set>
 </property>
</bean>
<bean id="emp1" class="com.gvace.collection.Employee">
 <property name="name" value="empA" />
</bean>
<bean id="emp2" class="com.gvace.collection.Employee">
 <property name="name" value="empB" />
</bean>

Map property injection config
Use the following properties to build <entry>
key
key-ref
value
value-ref

<bean id="department" class="com.gvace.collection.Department">
 <property name="name" value="Business"></property>
 <property name="employeeMap">
  <map>
   <entry key="1" value-ref="emp1"/>
   <entry key="2" value-ref="emp2"/>
</map>
 </property>
</bean>
<bean id="emp1" class="com.gvace.collection.Employee">
 <property name="name" value="empA" />
</bean>
<bean id="emp2" class="com.gvace.collection.Employee">
 <property name="name" value="empB" />
</bean>

Internal Bean

<bean id="department" class="com.gvace.Department">
  <property name="Manager">
    <bean class="com.gvace.Manager">
      <property name="name" value="managerA"/>
    </bean>
  </property>
</bean>

Inherit

<!-- Graduate extends Student -->
<bean id="student" class="com.gvace.impl.Student">
 <property name="name" value="studentA" />
 <property name="age" value="15" />
</bean>
<!-- use "parent" to set the properties from extending bean -->
<bean id="graduate" parent="student" class="com.gvace.impl.Graduate">
 <property name="degree" value="Master" />
</bean>

java.util.Properties

Properties implements Map
So we can load the Properties like the following

<bean id="department" class="com.gvace.impl.Department">
  <property name="pp">
    <props>
      <prop key="pp1">aaa</prop>
      <prop key="pp2">bbb</prop>
    </props>
  </property>
</bean>

NULL value

<property name="value">
  <null/>
</property>

Set properties by constructor

<bean id="employee" class="com.gvace.impl.Employee">
 <constructor-arg index="0" type="java.lang.String" value="empA"/>
 <constructor-arg index="1" type="int" value="15"/>
</bean>