Direct Value Injection

Bean properties and constructor arguments can be configured with literal values or references to other managed beans. The value attribute of the <property/> element accepts human-readable string representations, which Spring's conversion service transforms into the appropriate types.

Basic Value Assignment

<bean id="databaseConnection" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
    <property name="driverClassName" value="com.mysql.jdbc.Driver"/>
    <property name="url" value="jdbc:mysql://localhost:3306/appdb"/>
    <property name="username" value="admin"/>
    <property name="password" value="securepass123"/>
</bean>

P-Namespace Example

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:p="http://www.springframework.org/schema/p"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="databaseConnection" class="org.apache.commons.dbcp.BasicDataSource"
          destroy-method="close"
          p:driverClassName="com.mysql.jdbc.Driver"
          p:url="jdbc:mysql://localhost:3306/appdb"
          p:username="admin"
          p:password="securepass123"/>
</beans>

Properties Configuraton

<bean id="configProperties" 
      class="org.springframework.context.support.PropertySourcesPlaceholderConfigurer">
    <property name="properties">
        <value>
            database.driver=com.mysql.jdbc.Driver
            database.url=jdbc:mysql://localhost:3306/appdb
        </value>
    </property>
</bean>

Bean Reference Validation

The <idref/> element provides valdiation that the referenced bean exists during deploymant:

<bean id="serviceBean" class="..."/>

<bean id="clientBean" class="...">
    <property name="serviceIdentifier">
        <idref bean="serviceBean"/>
    </property>
</bean>

Cross-Bean References

The <ref/> element establishes dependencies between beans:

<ref bean="targetBean"/>

Parent Container References

<!-- Parent context -->
<bean id="paymentService" class="com.example.PaymentService"/>

<!-- Child context -->
<bean id="paymentService" class="org.springframework.aop.framework.ProxyFactoryBean">
    <property name="target">
        <ref parent="paymentService"/>
    </property>
</bean>

Inner Bean Definitions

<bean id="containerBean" class="...">
    <property name="nestedComponent">
        <bean class="com.example.Component">
            <property name="identifier" value="internal123"/>
            <property name="version" value="2.0"/>
        </bean>
    </property>
</bean>

Collection Configuration

<bean id="collectionHolder" class="example.CollectionContainer">
    <property name="emailMap">
        <map>
            <entry key="admin" value="admin@example.com"/>
            <entry key="support" value="help@example.com"/>
        </map>
    </property>
    <property name="itemList">
        <list>
            <value>first item</value>
            <ref bean="serviceBean"/>
        </list>
    </property>
</bean>

Collection Merging

<bean id="baseConfig" abstract="true" class="example.Configuration">
    <property name="settings">
        <map>
            <entry key="timeout" value="30"/>
            <entry key="retries" value="3"/>
        </map>
    </property>
</bean>

<bean id="extendedConfig" parent="baseConfig">
    <property name="settings">
        <map merge="true">
            <entry key="retries" value="5"/>
            <entry key="cacheSize" value="100"/>
        </map>
    </property>
</bean>

Strongly Typed Collections

public class DataProcessor {
    private Map<String, Double> thresholds;
    
    public void setThresholds(Map<String, Double> thresholds) {
        this.thresholds = thresholds;
    }
}

<bean id="processor" class="DataProcessor">
    <property name="thresholds">
        <map>
            <entry key="low" value="0.5"/>
            <entry key="high" value="95.0"/>
        </map>
    </property>
</bean>

Null Value Handling

<bean class="ExampleBean">
    <property name="optionalField">
        <null/>
    </property>
</bean>

C-Namespace for Constructor Injection

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:c="http://www.springframework.org/schema/c"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="mainService" class="com.example.MainService"
          c:repository-ref="dataRepository"
          c:timeout="5000"/>
</beans>

Nested Property Paths

<bean id="configBean" class="ConfigurationHolder">
    <property name="nested.config.value" value="finalSetting"/>
</bean>