如何在运行时创建多个 Jdbctemplate bean，指向不同的 Mysql 数据库？

Question

我需要为我的项目创建一个基于 SAAS 的版本：当新客户注册时，将为该特定客户创建一个新数据库；在我的 Spring Boot 代码中，需要在运行时为该客户端注册一个新的 JdbcTemplate bean。

已完成数据库部分的创建，但我需要知道是否有办法在运行时创建新的自定义 Jdbctemplate bean。

我已经有了为所有查询添加数据库前缀的想法，但我想知道还有其他可行的选择。

Answer 1

假设您已经找到了新的数据库凭据，下面的大纲将为您提供每个客户端的 JdbcTemplate。在以下代码中，所有相关数据点均以 cmets 的形式提及。

/**
 * uses a REQUEST scope with proxyMode as TARGET_CLASS to ensure wiring in spring context works
 * as it should for each and every request while caching created templates for full reuse.
 */
@Component
@Scope(value = WebApplicationContext.SCOPE_REQUEST, proxyMode = ScopedProxyMode.TARGET_CLASS)
public class TemplateResolver {
    @Autowired
    private TemplateCache cache;

    /**
     * You can inject current request OR any other bean for that matter here.
     * Assuming you are using Spring authenticaiotn object to get access to
     * current clientId. Adjust accordingly for your own use case
     */
    @Autowired
    private Authentication authentication;

    public JdbcTemplate getTemplate() {
        // TODO - extract this clientId from authenticaiton or any other means as appropriate
        Strnig clientId = null /* write your logic here */;
        return cache.getTemplate(clientId);
    }

}

/**
 * Caches created JdbcTemplate beans for further loockup and reuse as needed
 */
@Component
public class TemplateCache {
    private Map<String, JdbcTemplate> templates = new HashMap<String, JdbcTemplate>();

    @Autowired
    private ApplicationContext appContext;

    public JdbcTemplate getTemplate(String clientId) {
        if (templates.contains(clientId))
            return templates.get(clientId);
        return buildTemplate(clientId);
    }

    /**
     * This is a synchronized method to ensure concurrent requests DO NOT end
     * up creating multiple JdbcTempate objects.
     */
    private JdbcTemplate buildTemplate(String id) {
        // double check to ensure it's not already created by any other
        // concurrent request which finished its execution just now
        if (templates.contains(clientId))
            return templates.get(clientId);
        templates.put(clientId, appContext.getBean(JdbcTemplate.class, id));
        return templates.get(clientId);
    }
}

/**
 * uses a REQUEST scope with proxyMode as TARGET_CLASS to ensure wiring in spring context works
 * as it should for each and every request while caching created templates for full reuse.
 */
@Component
@Scope(value = WebApplicationContext.SCOPE_REQUEST, proxyMode = ScopedProxyMode.TARGET_CLASS)
public class TemplateResolver {
    @Autowired
    private TemplateCache cache;

    /**
     * You can inject current request OR any other bean for that matter here.
     * Assuming you are using Spring authenticaiotn object to get access to
     * current clientId. Adjust accordingly for your own use case
     */
    @Autowired
    private Authentication authentication;

    public JdbcTemplate getTemplate() {
        // TODO - extract this clientId from authenticaiton or any other means as appropriate
        String clientId = null /* write your logic here */;
        return cache.getTemplate(clientId);
    }

}

一旦完成上述操作，您必须注入 TemplateResolver 而不是直接在现有 bean 中注入 JdbcTempalate。每次调用JdbcTemplate 的任何方法时，将其替换为resolver.getTemplate().existingTemplateCall(...)