ApplicationInitlizer接口与Spring工具类-技术圈

项目中要灵活使用static来标记一些常用得类，static得作用就是跨对象得存在性。只要类没有被卸载掉，那么static修饰得属性就一直在。因此我们可以用static来标记一些引用，因为static一直存在，那么我们通过static得修饰就可以获得其引用得地址，不论被应用得对象身处何方。
有了上述思想，我们就能想到在spring框架中，上下文是我们重点关切得对象。因此我们想着通过static来引用spring上下文，然后形成一个工具类。我们在项目得业务部分能够通过该工具类来操作我们得spring上下文。这块我们说一下spring扩展接口ApplicationContextInitializer，这个接口会在spring上下文刷新之前进行调用，相当于提前将容器进行对外得暴露，当然页提供了我们修改其属性得权力。ApplicationContextInitializer得执行在prepareContext中，这块之前也大概得说过了。

我们通过查看源码，发现这块传入得是ConfigurableApplicationContext，注意这块返回得是空，意思是我们可以对这里得context进行应用标记。

protected void applyInitializers(ConfigurableApplicationContext context) {        Iterator var2 = this.getInitializers().iterator();        while(var2.hasNext()) {            ApplicationContextInitializer initializer = (ApplicationContextInitializer)var2.next();            Class requiredType = GenericTypeResolver.resolveTypeArgument(initializer.getClass(), ApplicationContextInitializer.class);            Assert.isInstanceOf(requiredType, context, "Unable to call initializer.");            initializer.initialize(context);        }}

通过以上得分析，我们就想这在initialize方法中将我们得上下文缓存进来。让我们来做个实践吧。

public class MyBean {
    private String name;
    private String config;
    public String getName() {        return name;    }
    public void setName(String name) {        this.name = name;    }
    public String getConfig() {        return config;    }

    public void setConfig(String config) {        this.config = config;    }
    @Override    public String toString() {        return "MyBean{" +                "name='" + name + '\'' +                ", config='" + config + '\'' +                '}';    }}

静态Spring工具类

public class MySpringContentUtils {

    public static ConfigurableApplicationContext context;

    public static ConfigurableApplicationContext getContext() {        return context;    }

    public static void setContext(ConfigurableApplicationContext context) {        MySpringContentUtils.context = context;    }

    public static void registerBean(String name, Class factoryClazz, Class beanClazz, MutablePropertyValues mpv) throws BeanDefinitionStoreException {        BeanDefinitionBuilder beanDefinitionBuilder = BeanDefinitionBuilder.genericBeanDefinition(beanClazz);        GenericBeanDefinition beanDefinition = (GenericBeanDefinition)beanDefinitionBuilder.getRawBeanDefinition();        beanDefinition.setBeanClass(factoryClazz == null ? beanClazz : factoryClazz);        beanDefinition.setPropertyValues(mpv);        BeanDefinitionRegistry beanFactory = (BeanDefinitionRegistry)context.getBeanFactory();        beanFactory.registerBeanDefinition(name, beanDefinition);    }

    public staticT getBean(String name) throws BeansException {        return (T) context.getBean(name);    }}

自定义initlizer接口

public class MyTianApplicationInitlize implements ApplicationContextInitializer {    @Override    public void initialize(ConfigurableApplicationContext configurableApplicationContext) {        System.out.println("我来了...宝");        MySpringContentUtils.setContext(configurableApplicationContext);    }}

测试类

    public static void main(String[] args) throws InterruptedException {        SpringApplication builder=new SpringApplicationBuilder(Demo1Application.class).initializers(new MyTianApplicationInitlize()).build();        builder.run( args);        System.out.println(env.toString());        MutablePropertyValues mpv = new MutablePropertyValues();        mpv.addPropertyValue("name","tianjingle_initlizer");        MySpringContentUtils.registerBean("lisi",null, MyBean.class,mpv);        MyBean myBean= (MyBean) MySpringContentUtils.getContext().getBean("lisi");        System.out.println(myBean.toString());    }

效果

通过上述实践，我们实现了我们得目标。当然我们也可以采用spring.factories文件得方式进行添加initlizer工具。这种方式在springBoot中得starter中用得比较多，看这里。

响应得修改我们得启动类

    public static void main(String[] args) throws InterruptedException {//        SpringApplication builder=new SpringApplicationBuilder(Demo1Application.class).initializers(new MyTianApplicationInitlize()).build();//        builder.run( args);        SpringApplication.run(Demo1Application.class,args);        System.out.println(env.toString());        MutablePropertyValues mpv = new MutablePropertyValues();        mpv.addPropertyValue("name","tianjingle_initlizer");        MySpringContentUtils.registerBean("lisi",null, MyBean.class,mpv);        MyBean myBean= (MyBean) MySpringContentUtils.getContext().getBean("lisi");        System.out.println(myBean.toString());    }

至于spring.factories文件得读取，这个在启动得时候springBoot就会加载。就说这么多吧。

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