Spring IoC and Bean

The org.springframework.beans and org.springframework.context packages are the basis for Spring Framework’s IoC container. The BeanFactory interface provides an advanced configuration mechanism capable of managing any type of object. ApplicationContext is a sub-interface of BeanFactory. It adds:

• Easier integration with Spring’s AOP features
• Message resource handling (for use in internationalization)
• Event publication
• Application-layer specific contexts such as the WebApplicationContext for use in web applications.

Create Config Get Beans

ApplicationContext context1 = new ClassPathXmlApplicationContex("services.xml");
ApplicationContext context2 = new GenericGroovyApplicationContext("services.groovy");
ApplicationContext context3 = FileSystemXmlApplicationContext("")

        ApplicationContext context = new ClassPathXmlApplicationContext("services.xml");

        // getBean
        DemoEntity entity1 = context.getBean("entity1", DemoEntity.class);

        System.out.println(entity1);

        DemoEntity entityAlias = context.getBean("entityAlias",DemoEntity.class);
        System.out.println(entityAlias);
        assert entity1 == entityAlias;
    

XML config attrs

<?xml version="1.0" encoding="UTF-8"?>
<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">

        <!-- factory-method -> public static factory method  -->
    <bean id="entity2" class="tech.realcpf.spring.dto.DemoEntity" factory-method="createInstance">
        <property name="name" value="jiacheng.liu"/>
        <property name="age" value="25"/>
    </bean>


    <!-- use    xmlns:p="http://www.springframework.org/schema/p"-->
    <bean id="entity3" class="tech.realcpf.spring.dto.DemoEntity"
        destroy-method="destroy"
        p:name="jc.liu"
        p:age="89">
        <!-- additional collaborators and configuration for this bean go here -->
    </bean>

    <!-- constructor-arg -->
    <bean id="entity1" class="tech.realcpf.spring.dto.DemoEntity">
        <constructor-arg type="java.lang.String" value="by constructor" name="name" index="0"></constructor-arg>
        <constructor-arg type="java.lang.Integer" value="123" name="age" index="1"></constructor-arg>
    </bean>

    <alias name="entity1" alias="entityAlias"></alias>

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

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

    <!-- init method -->
   <bean id="exampleInitBean" class="examples.ExampleBean" init-method="init"/>
   <!-- scope -->
   <bean id="exampleInitBean" class="examples.ExampleBean" scope="prototype"/>
</beans>

BeanPostProcessor

    private static final BeanPostProcessor beanPostProcessor = new BeanPostProcessor() {
        @Override
        public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
            return BeanPostProcessor.super.postProcessBeforeInitialization(bean, beanName);
        }

        @Override
        public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
            System.out.println("Bean '" + beanName + "' created : " + bean.toString());
            return BeanPostProcessor.super.postProcessAfterInitialization(bean, beanName);
        }
    };

    // PropertyOverrideConfigurer
    // PropertySourcesPlaceholderConfigurer
    
    private static final BeanFactoryPostProcessor beanFactoryPostProcessor = new BeanFactoryPostProcessor() {
        @Override
        public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {

        }
    };

Spring SPI

通过 resources/META-INF/spring.factories 作为SPI的配置文件
内容如下：
org.springframework.context.ApplicationContextInitializer=\
tech.realcpf.spring.DemoApplicationContextInitializer
org.springframework.context.ApplicationListener=\
tech.realcpf.spring.DemoApplicationListener


如果用spring-boot，再spring-boot3之后配置文件改成
 resources/META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports 作为SPI的配置文件
内容则是一个类一行

其中 org.springframework.boot.autoconfigure.AutoConfiguration 是Interface名

Spring Aop

https://docs.spring.io/spring-framework/reference/core/aop-api/pointcuts.html

Proxy - ProxyFactoryBean

        ApplicationContext context =
                new ClassPathXmlApplicationContext("aopdemo.xml");
        IDemoModel model = (IDemoModel) context.getBean("demoModelProxy");

        System.out.println(model.hello("jc.liu"));

<bean id="demoModelProxy"
   class="org.springframework.aop.framework.ProxyFactoryBean">
       <property name="proxyInterfaces">
           <list>
               <value>tech.realcpf.spring.aop.IDemoModel</value>
           </list>
       </property>

       <property name="target" ref="demoModelImpl">

       </property>

       <property name="interceptorNames">
           <list>
                <value>demoModelArgs</value> <!-- impl MethodBeforeAdvice -->
               <value>demoModelReturn</value> <!-- impl AfterReturningAdvice -->
           </list>
       </property>
   </bean>

Auto Proxy - BeanNameAutoProxyCreator

  ApplicationContext context =
                new ClassPathXmlApplicationContext("aopdemo.xml");
        IDemoModel demoModel = context.getBean(IDemoModel.class);
        System.out.println(demoModel.hello("jc.liu"));

 <bean class="org.springframework.aop.framework.autoproxy.BeanNameAutoProxyCreator">
                <property name="interceptorNames">
                    <list>
                        <value>demoModelArgs</value>
                        <value>demoModelReturn</value>
                    </list>
                </property>

        <!--        for auto match-->
        <property name="beanNames" value="*Model"></property>
    </bean>

Aspectj

    // call before
    @Before("tech.realcpf.spring.aop.aj.SystemArchitecture.service()")
    public void callBefore(JoinPoint joinPoint) {
        System.out.println("Before : " + Arrays.toString(joinPoint.getArgs()));
    }


    // call after
    @AfterReturning(pointcut = "tech.realcpf.spring.aop.aj.SystemArchitecture.service()",
            returning = "result")
    public void logResult(Object result) {
        System.out.println("after :" + result);
    }

    @Pointcut("execution(* tech.realcpf.spring.aop.aj..*(..))")
    public void service() {}

    <!-- enable aspectj -->
    <aop:aspectj-autoproxy/>
    

Spring EL

https://docs.spring.io/spring-framework/reference/core/expressions/evaluation.html

更多的语法语义

    static class Simple {
        public List<Boolean> booleans = new ArrayList<>();
    }

    ExpressionParser parser = new SpelExpressionParser();
    Expression exp = parser.parseExpression("'Hello World'.concat('!')");
    String message = (String) exp.getValue();
    System.out.println(message);
    System.out.println(
        parser.parseExpression("'hello'.bytes.length").getValue()
    );

    Simple simple = new Simple();
    simple.booleans.add(false);
    EvaluationContext context = SimpleEvaluationContext.forReadOnlyDataBinding().build();

    parser.parseExpression("booleans[0]")
            .setValue(context,simple,"true");
    assert simple.booleans.get(0);