1. Spring is lightweight= minimal impact
2. Spring DI= JavaBeans +interfaces
3.JSR-330=Dependency Injection for Java
4.JSR-303= Bean Validation API specification
5.
props = new Properties(); props.load(new FileInputStream(“ch2/src/conf/msf.properties”)); String rendererClass = props.getProperty(“renderer.class”);6.Injection vs. Lookup
7.<context:annotation-config>tag tells Spring to scan the codebase for dependency requirements.because of
<context:annotation-config>tag,
during the
initialization of Spring’s ApplicationContext, Spring will discover those @Autowired annotations and
inject the dependency (discovered via the <context:component-scan>tag) as required.
8.
@Value("John Smith")
private String name;
9.SpringEL
public class InjectSimpleConfig {
private String name = "John Smith";
private int age = 35;
private float height = 1.78f;
private boolean programmer = true;
private Long ageInSeconds = 1103760000L;
// Getter/setter method omitted
}
<bean id="injectSimpleConfig" class="com.apress.prospring3.ch4.xml.InjectSimpleConfig"/>
<bean id="injectSimpleSpel" class="com.apress.prospring3.ch4.xml.InjectSimpleSpel">
<property name="name">
<value>#{injectSimpleConfig.name}</value>
</property>
<property name="age">
<value>#{injectSimpleConfig.age + 1}</value>
</property>
<property name="height">
<value>#{injectSimpleConfig.height}</value>
</property>
<property name="isProgrammer">
<value>#{injectSimpleConfig.programmer}</value>
</property>
<property name="ageInSeconds">
<value>#{injectSimpleConfig.ageInSeconds}</value>
</property>
</bean>
@Service("injectSimpleSpel")
public class InjectSimpleSpel {
@Value("#{injectSimpleConfig.name}")
private String name;
@Value("#{injectSimpleConfig.age + 1}")
private int age;
@Value("#{injectSimpleConfig.height}")
private float height;
@Value("#{injectSimpleConfig.programmer}")
private boolean programmer;
@Value("#{injectSimpleConfig.ageInSeconds}")
private Long ageInSeconds;
// Other codes omitted
}
10.
Using Collections for Injection
public class CollectionInjection {
private Map<String, Object> map;
private Properties props;
private Set set;
private List list;
public static void main(String[] args) {
GenericXmlApplicationContext ctx = new GenericXmlApplicationContext();
ctx.load("classpath:app-context-xml.xml");
ctx.refresh();
CollectionInjection instance = (CollectionInjection) ctx.getBean("injectCollection");
instance.displayInfo();
}
public void setList(List list) {
this.list = list;
}
public void setSet(Set set) {
this.set = set;
}
public void setMap(Map <String, Object> map) {
this.map = map;
}
public void setProps(Properties props) {
this.props = props;
}
public void displayInfo() {
// display the Map
System.out.println("Map contents:\n");
for (Map.Entry<String, Object> entry: map.entrySet()) {
System.out.println("Key: " + entry.getKey() + " - Value: " + entry.getValue());
}
// display the properties
System.out.println("\nProperties contents:\n");
for (Map.Entry<Object, Object> entry: props.entrySet()) {
System.out.println("Key: " + entry.getKey() + " - Value: " + entry.getValue());
}
// display the set
System.out.println("\nSet contents:\n");
for (Object obj: set) {
System.out.println("Value: " + obj);
}
// display the list
System.out.println("\nList contents:\n");
for (Object obj: list) {
System.out.println("Value: " + obj);
}
}
}
<bean id="oracle" name="wiseworm" class="com.apress.prospring3.ch4.BookwormOracle"/> <bean id="injectCollection" class="com.apress.prospring3.ch4.xml.CollectionInjection"> <property name="map"> <map> <entry key="someValue"> <value>Hello World!</value> </entry> <entry key="someBean"> <ref local="oracle"/> </entry> </map> </property> <property name="props"> <props> <prop key="firstName">Clarence</prop> <prop key="secondName">Ho</prop> </props> </property> <property name="set"> <set> <value>Hello World!</value> <ref local="oracle"/> </set> </property> <property name="list"> <list> <value>Hello World!</value> <ref local="oracle"/> </list> </property> </bean>////////////////////////////////////////////////////////////////////////////////////////////////////////////
<util:map id="map" map-class="java.util.HashMap"> <entry key="someValue"> <value>Hello World!</value> </entry> <entry key="someBean"> <ref bean="oracle"/> </entry> </util:map> <util:properties id="props"> <prop key="firstName">Clarence</prop> <prop key="secondName">Ho</prop> </util:properties> <util:set id="set"> <value>Hello World!</value> <ref bean="oracle"/> </util:set> <util:list id="list"> <value>Hello World!</value> <ref bean="oracle"/> </util:list>
@Service("injectCollection")
public class CollectionInjection {
@Resource(name="map")
private Map<String, Object> map;
@Resource(name="props")
private Properties props;
@Resource(name="set")
private Set set;
@Resource(name="list")
private List list;
// Other codes omitted
}
11.Bean Scopes
Singleton:The default singleton scope.
Prototype:A new instance will be created by Spring when requested by application.
Request:For web application use. When using Spring MVC for web application,
beans with request scope will be instantiated for every HTTP request and then
destroyed when the request is completed.
Session:For web application use. When using Spring MVC for web applications,
beans with session scope will be instantiated for every HTTP session and then
destroyed when the session is over.
Global session:For portlet-based web applications. The global session scope beans
can be shared among all portlets withinthe same Spring MVC–powered portal
application.
Thread: A new bean instance will be created by Spring when requested by a new
thread, while for the same thread, the same bean instance will be returned. Note
that this scope is not registered by default.
Custom:Custom bean scope that can be created by implementing the interface
org.springframework.beans.factory.config.Scopeand registering the custom
scope in Spring’s configuration (for XML, use the class org.springframework.beans
.factory.config.CustomScopeConfigurer).