如何在Spring Boot中以编程方式创建bean？

Z时代
2024-01-10
分类：问答

我有一个应用程序，在application.properties中列出了许多数据源设置。我有一个@ConfigurationProperties可以加载这些设置的类。现在，我想从此类中获取值，ConfigurationProperties并使用它们来动态创建DataSource bean。我尝试使用@PostConstruct和实现BeanFactoryPostProcessor。但是，使用时BeanFactoryPostProcessor，处理似乎发生在早期-在ConfigurationProperties填充我的课程之前。如何DataSource使用Spring Boot" title="Spring Boot">Spring Boot快速读取属性并创建bean？

这是我的application.properties的样子：

ds.clients[0]=client1|jdbc:db2://server/client1
ds.clients[1]=client2,client3|jdbc:db2://server/client2
ds.clients[2]=client4|jdbc:db2://server/client4
ds.clients[3]=client5|jdbc:db2://server/client5

还有我的ConfigurationProperties类：

@Component
@ConfigurationProperties(prefix = "ds")
public class DataSourceSettings {
    public static Map<String, String> CLIENT_DATASOURCES = new LinkedHashMap<>();
    private List<String> clients = new ArrayList<>();
    public List<String> getClients() {
        return clients;
    }
    public void setClients(List<String> clients) {
        this.clients = clients;
    }
    @PostConstruct
    public void configure() {
        for (String client : clients) {
            // extract client name
            String[] parts = client.split("\\|");
            String clientName = parts[0];
            String url = parts[1];
            // client to datasource mapping
            String dsName = url.substring(url.lastIndexOf("/") + 1);
            if (clientName.contains(",")) {
                // multiple clients with same datasource
                String[] clientList = clientName.split(",");
                for (String c : clientList) {
                    CLIENT_DATASOURCES.put(c, dsName);
                }
            } else {
                CLIENT_DATASOURCES.put(clientName, dsName);
            }
        }
    }

在此@PostConstruct方法的结尾，我想BasicDataSource使用这些设置创建一个并将其添加到ApplicationContext。但是，如果我尝试通过实现BeanFactoryPostProcessor和实现来实现postProcessBeanFactory，则该clients属性为null，就像CLIENT_DATASOURCES我填充的一样@PostConstruct。

@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
    System.out.println("clients: " + CLIENT_DATASOURCES);
}

使用Spring Boot动态创建数据源的最佳方法是什么？

回答：

如何创建你的bean并要求Spring Boot向其中注入值？

就像是

@Bean
@ConfigurationProperties("ds.client1")
public DataSource dataSourceClient1() {
    DataSourceBuilder.create().build();
}
@Bean
@ConfigurationProperties("ds.client2")
public DataSource dataSourceClient2() {
    DataSourceBuilder.create().build();
}

然后，ds.client1名称空间中的任何设置都属于第一个数据源（即ds.client1.password该数据源的密码DataSource）。

但是，也许你不知道将拥有多少数据源？这变得越来越复杂，尤其是当你需要将那些动态数据源注入其他对象时。如果只需要按名称查找它们，则可以将它们自己注册为单例。这是一个有效的例子

@ConfigurationProperties(prefix = "ds")
public class DataSourceSettings implements BeanFactoryAware {
    private List<String> clients = new ArrayList<>();
    private BeanFactory beanFactory;
    public List<String> getClients() {
        return clients;
    }
    public void setClients(List<String> clients) {
        this.clients = clients;
    }
    @Override
    public void setBeanFactory(BeanFactory beanFactory) {
        this.beanFactory = beanFactory;
    }
    @PostConstruct
    public void configure() {
        Map<String, String> clientDataSources = new HashMap<String, String>();
        for (String client : clients) {
            // extract client name
            String[] parts = client.split("\\|");
            String clientName = parts[0];
            String url = parts[1];
            // client to datasource mapping
            String dsName = url.substring(url.lastIndexOf("/") + 1);
            if (clientName.contains(",")) {
                // multiple clients with same datasource
                String[] clientList = clientName.split(",");
                for (String c : clientList) {
                    clientDataSources.put(c, url);
                }
            }
            else {
                 clientDataSources.put(clientName, url);
            }
        }
        Assert.state(beanFactory instanceof ConfigurableBeanFactory, "wrong bean factory type");
        ConfigurableBeanFactory configurableBeanFactory = (ConfigurableBeanFactory) beanFactory;
        for (Map.Entry<String, String> entry : clientDataSources.entrySet()) {
            DataSource dataSource = createDataSource(entry.getValue());
            configurableBeanFactory.registerSingleton(entry.getKey(), dataSource);
        }
    }
    private DataSource createDataSource(String url) {
        return DataSourceBuilder.create().url(url).build();
    }
}