如何在Spring Boot中以编程方式创建bean？

Question

我有一个应用程序,其中包含application.properties中列出的许多数据源设置.我有一个@ConfigurationProperties加载这些设置的类.现在我想从这个ConfigurationProperties类中获取值并使用它们来动态创建DataSource bean.我尝试过使用@PostConstruct和实现BeanFactoryPostProcessor.但是,BeanFactoryPostProcessor处理似乎很早就发生了 - 在我的ConfigurationProperties课程填充之前.如何DataSource使用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

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);
            }
        }
    }

在这个@PostConstruct方法的最后,我想创建一个BasicDataSource带有这些设置并将其添加到ApplicationContext.但是,如果我尝试通过实现BeanFactoryPostProcessor和实现来执行此操作postProcessBeanFactory,则clients属性为null,就像CLIENT_DATASOURCES我填充的那样@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？

Answer 1

如何创建bean并请求Boot向其中注入值？

就像是

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

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

然后,ds.client1命名空间中的任何设置都属于第一个数据源(即ds.client1.password,该数据源的数据源密码DataSource).

但也许您不知道您将拥有多少数据源？这变得越来越复杂,特别是如果您需要在其他对象中注入这些动态数据源.如果您只需要按名称查找它们,您可以将它们自己注册为单身.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();
    }
}

请注意,这些bean 仅可通过bean名称查找获得.如果这对您有用,请告诉我.

Answer 2

我在github上创建了一个示例项目来演示你的用例.

https://github.com/lhotari/dynamic-datasources

我实现了一个ImportBeanDefinitionRegistrar来添加bean.您可以通过实施EnvironmentAware来获取配置.可能还有其他方法可以实现您的目标,但这是我在GspAutoConfiguration中用于动态注册bean的方式.GspAutoConfiguration使Grails GSP可用于Spring Boot应用程序.

以下是dynamic-datasource示例中的相关配置类:https: //github.com/lhotari/dynamic-datasources/blob/master/src/main/groovy/sample/DynamicDataSourcesConfiguration.java

package sample;

import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;

import org.springframework.beans.FatalBeanException;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.support.GenericBeanDefinition;
import org.springframework.boot.bind.PropertiesConfigurationFactory;
import org.springframework.context.EnvironmentAware;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
import org.springframework.core.env.ConfigurableEnvironment;
import org.springframework.core.env.Environment;
import org.springframework.core.type.AnnotationMetadata;
import org.springframework.jdbc.datasource.SingleConnectionDataSource;
import org.springframework.validation.BindException;

@Configuration
public class DynamicDataSourcesConfiguration implements ImportBeanDefinitionRegistrar, EnvironmentAware {
    private ConfigurableEnvironment environment;
    private static Map<String, Object> defaultDsProperties = new HashMap<String, Object>() {
        {
            put("suppressClose", true);
            put("username", "sa");
            put("password", "");
            put("driverClassName", "org.h2.Driver");
        }
    };

    @Override
    public void setEnvironment(Environment environment) {
        this.environment = (ConfigurableEnvironment)environment;
    }

    @Override
    public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
        DataSourceSettings settings = resolveSettings();
        for (Entry<String, String> entry : settings.clientDataSources().entrySet()) {
            createDsBean(registry, entry.getKey(), entry.getValue());
        }
    }

    private void createDsBean(BeanDefinitionRegistry registry, String beanName, String jdbcUrl) {
        GenericBeanDefinition beanDefinition = createBeanDefinition(SingleConnectionDataSource.class);
        beanDefinition.getPropertyValues().addPropertyValues(defaultDsProperties).addPropertyValue("url", jdbcUrl);
        registry.registerBeanDefinition(beanName, beanDefinition);
    }

    private GenericBeanDefinition createBeanDefinition(Class<?> beanClass) {
        GenericBeanDefinition beanDefinition = new GenericBeanDefinition();
        beanDefinition.setBeanClass(beanClass);
        beanDefinition.setAutowireMode(GenericBeanDefinition.AUTOWIRE_NO);
        return beanDefinition;
    }

    private DataSourceSettings resolveSettings() {
        DataSourceSettings settings = new DataSourceSettings();
        PropertiesConfigurationFactory<Object> factory = new PropertiesConfigurationFactory<Object>(settings);
        factory.setTargetName("ds");
        factory.setPropertySources(environment.getPropertySources());
        factory.setConversionService(environment.getConversionService());
        try {
            factory.bindPropertiesToTarget();
        }
        catch (BindException ex) {
            throw new FatalBeanException("Could not bind DataSourceSettings properties", ex);
        }
        return settings;
    }

}