深入分析Spring BeanDefinition的构造元信息

<bean id="user" class="org.thinging.in.spring.ioc.overview.domain.User">
  <property name="id" value="1"/>
  <property name="name" value="Liutx"/>
</bean>

@Service(value = "HelloService")
public class HelloService {

    private final Logger logger = LoggerFactory.getLogger(HelloService.class);

    private final HelloAsyncService helloAsyncService;

        public HelloService(HelloAsyncService helloAsyncService) {
        this.helloAsyncService = helloAsyncService;
    }
}

@Component(value = "balanceRedisProcessor")
public class BalanceRedisProcessorService implements EntryHandler<Balance>, Runnable {

    @Autowired(required = true)
    public BalanceRedisProcessorService(RedisUtils redisUtils,
                                        CanalConfig canalConfig,
                                        @Qualifier("ownThreadPoolExecutor") Executor executor, RocketMQProducer rocketMqProducer) {
        this.redisUtils = redisUtils;
        this.canalConfig = canalConfig;
        this.executor = executor;
        this.rocketMQProducer = rocketMqProducer;
    }
}

private final ThreadLocal<Set<EncodedResource>> resourcesCurrentlyBeingLoaded =
        new NamedThreadLocal<Set<EncodedResource>>("XML bean definition resources currently being loaded"){
            @Override
            protected Set<EncodedResource> initialValue() {
                return new HashSet<>(4);
            }
        };

/**
 * Load bean definitions from the specified XML file.
 * @param encodedResource the resource descriptor for the XML file,
 * allowing to specify an encoding to use for parsing the file
 * @return the number of bean definitions found
 * @throws BeanDefinitionStoreException in case of loading or parsing errors
 */
public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException {
    Assert.notNull(encodedResource, "EncodedResource must not be null");
    if (logger.isTraceEnabled()) {
        logger.trace("Loading XML bean definitions from " + encodedResource);
    }

    Set<EncodedResource> currentResources = this.resourcesCurrentlyBeingLoaded.get();

    if (!currentResources.add(encodedResource)) {
        throw new BeanDefinitionStoreException(
                "Detected cyclic loading of " + encodedResource + " - check your import definitions!");
    }

    try (InputStream inputStream = encodedResource.getResource().getInputStream()) {
        InputSource inputSource = new InputSource(inputStream);
        if (encodedResource.getEncoding() != null) {
            inputSource.setEncoding(encodedResource.getEncoding());
        }
        // 实际上从指定的 XML 文件加载 Bean 定义
        return doLoadBeanDefinitions(inputSource, encodedResource.getResource());
    }
    catch (IOException ex) {
        throw new BeanDefinitionStoreException(
                "IOException parsing XML document from " + encodedResource.getResource(), ex);
    }
    finally {
        currentResources.remove(encodedResource);
        if (currentResources.isEmpty()) {
            this.resourcesCurrentlyBeingLoaded.remove();
        }
    }
}


//实际上从指定的 XML 文件加载 Bean 定义
/**
 * Actually load bean definitions from the specified XML file.
 * @param inputSource the SAX InputSource to read from
 * @param resource the resource descriptor for the XML file
 * @return the number of bean definitions found
 * @throws BeanDefinitionStoreException in case of loading or parsing errors
 * @see #doLoadDocument
 * @see #registerBeanDefinitions
 */
protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)
        throws BeanDefinitionStoreException {

    try {
        Document doc = doLoadDocument(inputSource, resource);
        int count = registerBeanDefinitions(doc, resource);
        if (logger.isDebugEnabled()) {
            logger.debug("Loaded " + count + " bean definitions from " + resource);
        }
        return count;
    }
}

public class User {

    private Long id;

    private String name;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + ''' +
                '}';
    }
}

//通过BeanDefinitionBuilder构建
BeanDefinitionBuilder beanDefinitionBuilder = BeanDefinitionBuilder.genericBeanDefinition(User.class);
//通过属性设置
beanDefinitionBuilder.addPropertyValue("id", 1L)
        .addPropertyValue("name","公众号：种棵代码技术树");

//获取BeanDefinition实例
BeanDefinition beanDefinition = beanDefinitionBuilder.getBeanDefinition();
// BeanDefinition 并非 Bean 终态，可以自定义修改
System.out.println(beanDefinition);

// 2. 通过 AbstractBeanDefinition 以及派生类
GenericBeanDefinition genericBeanDefinition = new GenericBeanDefinition();
//设置Bean类型
genericBeanDefinition.setBeanClass(User.class);
//通过 MutablePropertyValues 批量操作属性
MutablePropertyValues propertyValues = new MutablePropertyValues();
propertyValues.add("id",1L)
        .add("name","公众号：种棵代码技术树");
// 通过 set MutablePropertyValues 批量操作属性
genericBeanDefinition.setPropertyValues(propertyValues);