Spring核心技术IoC容器（四）

使用 depends-on

<ref/>

depends-on

depends-on

<bean id="beanOne" class="ExampleBean" depends-on="manager"/>
<bean id="manager" class="ManagerBean" />

depends-on

<bean id="beanOne" class="ExampleBean" depends-on="manager,accountDao">
<property name="manager" ref="manager" />
</bean>

<bean id="manager" class="ManagerBean" />
<bean id="accountDao" class="x.y.jdbc.JdbcAccountDao" />

depends-on

depends-on

depends-on

depends-on

延迟初始化的Bean

ApplicationContext

<bean/>

lazy-init

<bean id="lazy" class="com.foo.ExpensiveToCreateBean" lazy-init="true"/>
<bean name="not.lazy" class="com.foo.AnotherBean"/>

ApplicationContext

lazy

ApplicationContext

ApplicationContxt

ApplicationContext

<beans/>

default-lazy-init

<beans default-lazy-init="true">
<!-- no beans will be pre-instantiated... -->
</beans>

自动装配关联

ApplicationContext

<bean/>

autowire

ref

master

setMaster(..)

master

String

Map

Map

Map

自动装配的限制和劣势

property

constructor-arg

autowire-candidate

false

<bean/>

primary

true

排除一个Bean，使之不自动装配

<bean/>

autowire-candidate

false

@Autowired

<beans/>

default-autowire-candidates

*Repository

autowire-candidate

方法注入

ApplicationContextAware

ApplicationContext

getBean("B")

// a class that uses a stateful Command-style class to perform some processing
package fiona.apple;

// Spring-API imports
import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;

public class CommandManager implements ApplicationContextAware {

private ApplicationContext applicationContext;

public Object process(Map commandState) {
// grab a new instance of the appropriate Command
Command command = createCommand();
// set the state on the (hopefully brand new) Command instance
command.setState(commandState);
return command.execute();
}

protected Command createCommand() {
// notice the Spring API dependency!
return this.applicationContext.getBean("command", Command.class);
}

public void setApplicationContext(
ApplicationContext applicationContext) throws BeansException {
this.applicationContext = applicationContext;
}
}

查找方法注入

final

final

@Bean

CommandManager

createCommand()

CommandManager

package fiona.apple;

// no more Spring imports!

public abstract class CommandManager {

public Object process(Object commandState) {
// grab a new instance of the appropriate Command interface
Command command = createCommand();
// set the state on the (hopefully brand new) Command instance
command.setState(commandState);
return command.execute();
}

// okay... but where is the implementation of this method?
protected abstract Command createCommand();
}

<public|protected> [abstract] <return-type> theMethodName(no-arguments);

<!-- a stateful bean deployed as a prototype (non-singleton) -->
<bean id="command" class="fiona.apple.AsyncCommand" scope="prototype">
<!-- inject dependencies here as required -->
</bean>

<!-- commandProcessor uses statefulCommandHelper -->
<bean id="commandManager" class="fiona.apple.CommandManager">
<lookup-method name="createCommand" bean="command"/>
</bean>

createCommand()

command

任意的方法替换

replaced-method

public class MyValueCalculator {

public String computeValue(String input) {
// some real code...
}

// some other methods...

}

org.springframework.beans.factory.support.MethodReplacer

/**
* meant to be used to override the existing computeValue(String)
* implementation in MyValueCalculator
*/
public class ReplacementComputeValue implements MethodReplacer {

public Object reimplement(Object o, Method m, Object[] args) throws Throwable {
// get the input value, work with it, and return a computed result
String input = (String) args[0];
...
return ...;
}
}

<bean id="myValueCalculator" class="x.y.z.MyValueCalculator">
<!-- arbitrary method replacement -->
<replaced-method name="computeValue" replacer="replacementComputeValue">
<arg-type>String</arg-type>
</replaced-method>
</bean>

<bean id="replacementComputeValue" class="a.b.c.ReplacementComputeValue"/>

<replaced-method>

<arg=type/>

java.lang.String

java.lang.String
String
Str