Spring Boot从Bean中的数据库预加载数据 [英] Spring boot preloading data from database in bean

问题描述

我要在一个表中请求具有递归关系的元素：

I'm asking for elements that have a recursive relationship in one table:

子ID |家长ID

1 | null

2 | 1

3 | 1

4 | 2

以此类推...要询问整个数据结构，大约需要10秒钟。目前我无法重新设计该表，因为它花费了太多时间（对于更多信息：递归ORM类的Spring Repository性能问题）

And so on...To ask for this whole datastructure it takes about 10 secondsAt the moment I can't redesign this table because it cost too much time (for more information: Spring Repository performance issues with recursive ORM Class)

现在，我正在考虑在春季启动期间在Bean中预加载所有数据，以便客户端与Bean通信，并更新Bean和数据库中的数据。 。我认为启动该公司要花多长时间并不重要，但是用户必须等待它的答案才有多长。

Now, I am thinking about preloading all data during spring startup in a bean, so that the client "communicates" with the bean and I update the data in bean and database. I think it doesn't matter how long this startup takes, but it matters how long the user has to wait for its answer.

到目前为止，我没有无法对其进行预加载。我试图创建一个像这样的bean：

public class AppConfig extends WebMvcConfigurerAdapter {
...
@Autowired
SkillDAO skillDAO
...
@Bean(name="allSkills")
public List<Skill> allSkills(){
    return skillDAO.findBySkill(null);
}
...

它不起作用，因为我得到了错误：

It doesn't work cause I get an error:

原因：org.springframework.beans.factory.BeanCurrentlyInCreationException：创建名称为 dataSource的bean时出错：请求的bean当前为在创建中：是否存在无法解析的循环引用？

Caused by: org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'dataSource': Requested bean is currently in creation: Is there an unresolvable circular reference?

顺便说一下，我在AppConfig中创建了所有bean。当我删除此 allSkills bean时，它再次起作用。

By the way, I create all my beans in AppConfig. When I delete this "allSkills" bean, it works again.

更新

@Component
public class MyListener {

@Autowired
private SkillDAO skillDAO;

@EventListener
public void onApplicationReady(ApplicationReadyEvent ready) {
    System.out.println("++++++++++++++ HALLO +++++++++++++");
    skillDAO.findBySkill(null);
}
}

...

@Bean(name="skillBean")
public MyListener myListener() {
    return new MyListener();
}

推荐答案

A 缓存可以轻松解决您的需求。

A Cache would solve your requirement elegantly.

理想情况下，您将拥有 Service

Ideally you would have a Service which has a method which returns the skills.

此方法看起来像这样：

import org.springframework.cache.annotation.Cacheable;

@Cacheable(value = "skills", key = "#root.methodName")
public List<Skill> getAllSkills() {
    return ... your skills ...;
}

要在Spring Boot中启用缓存，请添加 @在配置类中启用EnableCaching 批注，并添加 Bean 进行配置：

To enable Caching in Spring Boot, add the @EnableCaching annotation to your configurations class, and add a Bean to configure it:

import org.springframework.cache.CacheManager;
import org.springframework.cache.annotation.EnableCaching;
import org.springframework.cache.concurrent.ConcurrentMapCacheManager;

@Bean
public CacheManager cacheManager() {
    return new ConcurrentMapCacheManager("skills", "othercachename");
}

这样，方法 getAllSkills 仅在第一次调用时执行一次，然后从缓存管理器返回值，甚至不调用该方法。

This way, the method getAllSkills is just executed once, the first time it's called, and afterwards the values are returned from the cache-manager without even calling the method.

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