SpringBoot上下文初始器加载过程详解
程序员文章站
2022-06-09 09:21:38
利用 spring 工厂加载机制，实例化 applicationcontextinitializer 实现类，并排序对象集合。关键方法private collection
利用 spring 工厂加载机制，实例化 applicationcontextinitializer 实现类，并排序对象集合。
关键方法
private <t> collection<t> getspringfactoriesinstances(class<t> type,
class<?>[] parametertypes, object... args) {
classloader classloader = thread.currentthread().getcontextclassloader();
// use names and ensure unique to protect against duplicates
set<string> names = new linkedhashset<>(
springfactoriesloader.loadfactorynames(type, classloader));
list<t> instances = createspringfactoriesinstances(type, parametertypes,
classloader, args, names);
annotationawareordercomparator.sort(instances);
return instances;
}
技术实现步骤
- 实现类： org.springframework.core.io.support.springfactoriesloader
- 配置资源： meta-inf/spring.factories
- 排序： annotationawareordercomparator#sort
自定义初始化器
编写类实现applicationcontextinitializer接口
有两种指定顺序的方法,第一种:类上加注解@order(ordered.highest_precedence),第二种则是实现ordered接口
@order(ordered.highest_precedence)
public class helloworldapplicationcontextinitializer<c extends configurableapplicationcontext>
implements applicationcontextinitializer<c> {
@override
public void initialize(c applicationcontext) {
system.out.println("configurableapplicationcontext.id = "+ applicationcontext.getid());
}
}
public class afterhelloworldapplicationcontextinitializer implements applicationcontextinitializer, ordered {
@override
public void initialize(configurableapplicationcontext applicationcontext) {
system.out.println("after application.id = " + applicationcontext.getid());
}
@override
public int getorder() {
return ordered.lowest_precedence;
}
}
在spring.properties中配置
# applicationcontextinitializer
org.springframework.context.applicationcontextinitializer=\
com.imooc.diveinspringboot.context.afterhelloworldapplicationcontextinitializer,\
com.imooc.diveinspringboot.context.helloworldapplicationcontextinitializer
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