Java 如何在Spring中获取@Component的实例？

我有一个名为RegistrationValidator的@Container类，它依赖于spring@存储库。通过自动连接在服务或其他容器中获取它的实例是可以的，但我需要在常规POJO中访问它。如何在不将所有POJO转换为@Container或@Service对象的情况下获取该验证器的实例。是否有一种方法可以在RegistrationValidator中添加一个返回实例的静态getInstance方法

package core.dao.validator;

import core.dao.Registration;
import core.repository.RegistrationRepository;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.stereotype.Component;
import org.springframework.validation.Errors;
import org.springframework.validation.ValidationUtils;
import org.springframework.validation.Validator;

/**
 * Validates the Registration DAO.
 *
 * @author Srini Katragadda
 */
@Component
public class RegistrationValidator implements Validator {
    private static final Logger LOGGER = LoggerFactory.getLogger(RegistrationValidator.class);
    private static final int MAX_SIZE = 255;

    private final RegistrationRepository repository;

    @Autowired
    RegistrationValidator(RegistrationRepository repository) {
        this.repository = repository;
    }

    @Override
    public boolean supports(Class clazz) {
        return Registration.class.equals(clazz);
    }

    @Override
    public void validate(Object obj, Errors errors) {
        Registration registration = (Registration) obj;

        // Validate Message Id
        ValidationUtils.rejectIfEmpty(errors, "messageId", "messageId.empty");
        if (registration.getMessageId() != null &&
                registration.getMessageId().length() > MAX_SIZE) 
            errors.rejectValue("messageId", "Size greater than " + MAX_SIZE);

        // Validate for duplicate messageId information
        if (hasDuplicateMessageIdInDatabase(registration)) {
            errors.rejectValue("callouts", "Database has duplicate registration with messageId.");
        }

    }

    /**
     * Check if there is duplicate messageId in database.
     */
    private boolean hasDuplicateMessageIdInDatabase(Registration adsRegistration) {
        return (repository.findByMessageId(adsRegistration.getMessageId()) != null);
    }
}

这里我需要一个验证器的实例。签出Builder.build（）方法，该方法将验证器实例传递给实用程序方法。在我需要在RegistrationValidator中自动连接@Repository之前，这一切都很好。现在，我需要传递repository的实例，以便能够构造验证器，我想知道如何在不使DAO本身成为另一个组件并将其与RegistrationValidator自动连接的情况下

package core.dao;

import core.dao.validator.RegistrationValidator;
import core.util.ValidatorUtil;
import core.util.ToString;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;

/**
 * The data access object that holds the information of an Registration.
 */
@JsonIgnoreProperties(ignoreUnknown = true)
public final class Registration {

    private String id;
    private String messageId;
    private String version;

    public Registration() {
    }

    private Registration(Builder builder) {
        this.id = builder.id;
        this.messageId = builder.messageId;
        this.version = builder.version;
    }

    public static Builder getBuilder() {
        return new Builder();
    }

    public String getId() {
        return id;
    }

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

    public String getMessageId() {
        return messageId;
    }

    public void setMessageId(String messageId) {
        this.messageId = messageId;
    }

    public String getVersion() {
        return version;
    }

    public void setVersion(String version) {
        this.version = version;
    }

    /**
     * Builder pattern makes the object easier to construct in one line.
     */
    public static class Builder {

        private String id;

        private String messageId;

        private String version;

        private Builder() {}

        public Builder id(String id) {
            this.id = id;
            return this;
        }

        public Builder messageId(String messageId) {
            this.messageId = messageId;
            return this;
        }


        public Builder version(String version) {
            this.version = version;
            return this;
        }

        public Registration build() {
            Registration entry = new Registration(this);
            return (Registration) ValidatorUtil.validate(entry, new RegistrationValidator());
        }
    }
}

下面是ValidatorUtil.validate代码的完整性

public static Object validate(Object entry, org.springframework.validation.Validator customValidator) {
    Errors errors = new BeanPropertyBindingResult(entry, entry.getClass().getName());
    customValidator.validate(entry, errors);
    if (errors == null || errors.getAllErrors().isEmpty())
        return entry;
    else {
        LOGGER.error(errors.toString());
        throw new InvalidDataException(errors.getAllErrors().toString(), errors);
    }
}

---

您可以使用SpringBeanAuthoringSupport将SpringBean自动连接到pojo中，方法如下：

public class Pojo {

@Autowired
private RegistrationRepository repository

    public void methodWhichRequiresBean() {

        SpringBeanAutowiringSupport.processInjectionBasedOnCurrentContext(this);

        repository.doStuff()

     }

---

希望这有帮助

为什么要在POJO中使用它的实例？你能展示用例吗？可能是可以移动到服务类的。更新了问题并提供了更多信息。请看一看。谢谢。理想情况下，我不会让

validate（）

方法与DB对话以验证重复项。它应该只验证对象的状态（无论它是否处于有效状态）。就这样。在那之后，服务层的工作是验证完全构造和验证的对象是否重复。是的，可能这就是我要做的，以保持它干净。在一个地方进行所有验证有一定的优点，但不会以污染代码为代价。感谢您的帮助。repository.doStuff（）将返回NullPointerException，因此存储库未初始化。Pojo可能是在spring初始化此bean之前创建的吗？在这个问题上，我遇到了类似的问题：我的问题是，我在构造函数中使用了SpringBeanAuthoringSupport，而bean仍然没有创建。我的POJO是在注入另一个Spring服务的Spring管理工厂中创建的——无论如何，问题在于POJO/bean的创建时间。