如何在Spring Boot中以编程方式创建bean？

2 回答

• 10

  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 是该 DataSource 的数据源密码） .

  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，通过bean名称查找可以使用这些bean only . 如果这对您有用，请告诉我 .

  回复于 2024-04-30T14:19:32+08:00
• 19

  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ImportBeanDefinitionRegistrar来添加bean . 您可以通过实现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 .

  这是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;
      }
  
  }
  

  回复于 2024-04-30T14:19:32+08:00