Spring5 中更优雅的第三方 Bean 注入

/**
 * Specify a callback for creating an instance of the bean,
 * as an alternative to a declaratively specified factory method.
 * <p>If such a callback is set, it will override any other constructor
 * or factory method metadata. However, bean property population and
 * potential annotation-driven injection will still apply as usual.
 * @since 5.0
 * @see #setConstructorArgumentValues(ConstructorArgumentValues)
 * @see #setPropertyValues(MutablePropertyValues)
 */
public void setInstanceSupplier(@Nullable Supplier<?> instanceSupplier) {
	this.instanceSupplier = instanceSupplier;
}

/**
 * Return a callback for creating an instance of the bean, if any.
 * @since 5.0
 */
@Nullable
public Supplier<?> getInstanceSupplier() {
	return this.instanceSupplier;
}

OkHttpClient client = new OkHttpClient.Builder()
        .connectTimeout(5, TimeUnit.SECONDS)
        .readTimeout(5, TimeUnit.SECONDS)
        .build();
Request getReq = new Request.Builder().get().url("http://www.javaboy.org").build();
Call call = client.newCall(getReq);
call.enqueue(new Callback() {
    @Override
    public void onFailure(@NotNull Call call, @NotNull IOException e) {
        System.out.println("e.getMessage() = " + e.getMessage());
    }
    @Override
    public void onResponse(@NotNull Call call, @NotNull Response response) throws IOException {
        System.out.println("response.body().string() = " + response.body().string());
    }
});

public class OkHttpStaticFactory {
    private static OkHttpClient okHttpClient;
    static {
        okHttpClient = new OkHttpClient.Builder()
                .connectTimeout(5, TimeUnit.SECONDS)
                .readTimeout(5, TimeUnit.SECONDS)
                .build();
    }
    
    public static OkHttpClient getOkHttpClient() {
        return okHttpClient;
    }
}

public class OkHttpInstanceFactory {
    private volatile static OkHttpClient okHttpClient;

    public OkHttpClient getInstance() {
        if (okHttpClient == null) {
            synchronized (OkHttpInstanceFactory.class) {
                if (okHttpClient == null) {
                    okHttpClient = new OkHttpClient.Builder()
                            .connectTimeout(5, TimeUnit.SECONDS)
                            .readTimeout(5, TimeUnit.SECONDS)
                            .build();
                }
            }
        }
        return okHttpClient;
    }
}

public class OkHttpClientFactoryBean implements FactoryBean<OkHttpClient> {
    @Override
    public OkHttpClient getObject() throws Exception {
        return new OkHttpClient.Builder()
                .connectTimeout(5, TimeUnit.SECONDS)
                .readTimeout(5, TimeUnit.SECONDS)
                .build();
    }

    @Override
    public Class<?> getObjectType() {
        return OkHttpClient.class;
    }

    @Override
    public boolean isSingleton() {
        return true;
    }
}

@Override
public Object instantiate(RootBeanDefinition bd, @Nullable String beanName, BeanFactory owner,
		@Nullable Object factoryBean, final Method factoryMethod, Object... args) {
		ReflectionUtils.makeAccessible(factoryMethod);
		Method priorInvokedFactoryMethod = currentlyInvokedFactoryMethod.get();
		try {
			currentlyInvokedFactoryMethod.set(factoryMethod);
			Object result = factoryMethod.invoke(factoryBean, args);
			if (result == null) {
				result = new NullBean();
			}
			return result;
		}
		finally {
			if (priorInvokedFactoryMethod != null) {
				currentlyInvokedFactoryMethod.set(priorInvokedFactoryMethod);
			}
			else {
				currentlyInvokedFactoryMethod.remove();
			}
		}
}

AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext();
GenericBeanDefinition definition = new GenericBeanDefinition();
definition.setBeanClass(Book.class);
definition.setInstanceSupplier((Supplier<Book>) () -> {
    Book book = new Book();
    book.setName("深入浅出 Spring Security");
    book.setAuthor("江南一点雨");
    return book;
});
ctx.registerBeanDefinition("b1", definition);
ctx.refresh();
Book b = ctx.getBean("b1", Book.class);
System.out.println("b = " + b);

public class BookSupplier {
    public Book getBook() {
        Book book = new Book();
        book.setName("深入浅出 Spring Security");
        book.setAuthor("江南一点雨");
        return book;
    }
}

AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext();
GenericBeanDefinition definition = new GenericBeanDefinition();
definition.setBeanClass(Book.class);
BookSupplier bookSupplier = new BookSupplier();
definition.setInstanceSupplier(bookSupplier::getBook);
ctx.registerBeanDefinition("b1", definition);
ctx.refresh();
Book b = ctx.getBean("b1", Book.class);
System.out.println("b = " + b);

protected BeanWrapper createBeanInstance(String beanName, RootBeanDefinition mbd, @Nullable Object[] args) {
	// Make sure bean class is actually resolved at this point.
	Class<?> beanClass = resolveBeanClass(mbd, beanName);
	if (beanClass != null && !Modifier.isPublic(beanClass.getModifiers()) && !mbd.isNonPublicAccessAllowed()) {
		throw new BeanCreationException(mbd.getResourceDescription(), beanName,
				"Bean class isn't public, and non-public access not allowed: " + beanClass.getName());
	}
	Supplier<?> instanceSupplier = mbd.getInstanceSupplier();
	if (instanceSupplier != null) {
		return obtainFromSupplier(instanceSupplier, beanName);
	}
	if (mbd.getFactoryMethodName() != null) {
		return instantiateUsingFactoryMethod(beanName, mbd, args);
	}
	//...
	return instantiateBean(beanName, mbd);
}

@Nullable
private Object obtainInstanceFromSupplier(Supplier<?> supplier, String beanName) {
	String outerBean = this.currentlyCreatedBean.get();
	this.currentlyCreatedBean.set(beanName);
	try {
		if (supplier instanceof InstanceSupplier<?> instanceSupplier) {
			return instanceSupplier.get(RegisteredBean.of((ConfigurableListableBeanFactory) this, beanName));
		}
		if (supplier instanceof ThrowingSupplier<?> throwableSupplier) {
			return throwableSupplier.getWithException();
		}
		return supplier.get();
	}
}