如何为AbstractRoutingDataSource制作安全频繁的DataSource开关？

问题描述

我根据。我有几个数据库具有相同的结构，我需要选择哪个数据库将运行每个特定的查询。

本地主机上的一切工作正常，但我担心这将如何在真实的网站环境中。他们正在使用一些静态上下文持有者来确定使用哪个数据源：

  public class CustomerContextHolder {
 
私有静态最终ThreadLocal< CustomerType> contextHolder = 
 new ThreadLocal< CustomerType>（）; 
 
 public static void setCustomerType（CustomerType customerType）{
 Assert.notNull（customerType，customerType不能为null）; 
 contextHolder.set（customerType）; 
 
 
 public static CustomerType getCustomerType（）{
 return（CustomerType）contextHolder.get（）; 
 
 
 public static void clearCustomerType（）{
 contextHolder.remove（）; 
 
 
 
 
 $ b 
它被包装在一些ThreadLocal容器中，但究竟是什么这是否意味着？当两个Web请求并行调用这段代码时会发生什么： 
 
 
  CustomerContextHolder.setCustomerType（CustomerType.GOLD）; 
 //<另一个用户将在这里将客户类型切换到另一个请求中的CustomerType.SILVER> 
列表<项目> goldItems = catalog.getItems（）; 
  
每个Web请求都被包装到Spring MVC的自己的线程中吗？其他Web用户可以看到 CustomerContextHolder.setCustomerType（）更改吗？我的控制器有 synchronizeOnSession = true 。
 
 
如何确保没有人会切换数据源，直到我运行所需的查询
 
 
谢谢。
 
 
是的，但是这与Spring MVC没有任何关系，容器正在这样做（容器有一个线程池，并选择其中一个来处理每个请求）。  
 
 
没有。 是线程本地的。从javadoc：
 
 
你在 ThreadLocal 中设置 code>对其他线程不可见。你应该很好
 
I implemented Dynamic DataSource Routing  for Spring+Hibernate according to this article. I have several databases with same structure and I need to select which db will run each specific query.
Everything works fine on localhost, but I am worrying about how this will hold up in real web site environment. They are using some static context holder to determine which datasource to use:
public class  CustomerContextHolder {

   private static final ThreadLocal<CustomerType> contextHolder =
            new ThreadLocal<CustomerType>();

   public static void setCustomerType(CustomerType customerType) {
      Assert.notNull(customerType, "customerType cannot be null");
      contextHolder.set(customerType);
   }

   public static CustomerType getCustomerType() {
      return (CustomerType) contextHolder.get();
   }

   public static void clearCustomerType() {
      contextHolder.remove();
   }
}
It is wrapped inside some ThreadLocal container, but what exactly does that mean? What will happen when two web requests call this piece of code in parallel:
CustomerContextHolder.setCustomerType(CustomerType.GOLD);
//<another user will switch customer type here to CustomerType.SILVER in another request>
List<Item> goldItems = catalog.getItems();
Is every web request wrapped into its own thread in Spring MVC? Will CustomerContextHolder.setCustomerType() changes be visible to other web users? My controllers have synchronizeOnSession=true.
How to make sure that nobody else will switch datasource until I run required query for current user?
Thanks.
 解决方案 
Yes, but this has nothing to do with Spring MVC, the container is doing that (the container has a thread pool and picks one of the them to handle each request). 
No. A ThreadLocal is by definition local to a thread. From the javadoc:
What you set in a ThreadLocal is not visible to other threads. You should be fine
                        
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