@value注解

README.md

@@ -41,7 +41,8 @@ If this project can help you, please give a **STAR, thank you!!!**
 #### Expanding 
 * [PropertyPlaceholderConfigurer](#PropertyPlaceholderConfigurer)
 * [Package scan](#包扫描)
-* [@Autowired and @Value annotation](#基于注解@Autowired和@Value的依赖注入)
+* [@Value annotation](#@Value annotation)
+* [@Autowired annotation](#@Autowired annotation)
 * [Type conversion](#类型转换)
 
 #### Advanced

README_CN.md

@@ -41,7 +41,8 @@
 #### 扩展篇
 * [PropertyPlaceholderConfigurer](#PropertyPlaceholderConfigurer)
 * [包扫描](#包扫描)
-* [基于注解@Autowired和@Value的依赖注入](#基于注解@Autowired和@Value的依赖注入)
+* [@Value注解](#@Value注解)
+* [基于注解@Autowired的依赖注入](#基于注解@Autowired的依赖注入)
 * [类型转换](#类型转换)
 
 #### 高级篇

changelog.md

@@ -1018,11 +1018,58 @@ public class PackageScanTest {
 }
 ```
 
+## @Value注解
+> 分支：value-annotation
 
+注解@Value和@Autowired通过BeanPostProcessor处理。InstantiationAwareBeanPostProcessor增加postProcessPropertyValues方法，在bean实例化之后设置属性之前执行，查看AbstractAutowireCapableBeanFactory#doCreateBean方法。
 
+增加AutowiredAnnotationBeanPostProcessor用于处理注解@Value，@Autowired的处理在下一节实现，在ClassPathBeanDefinitionScanner#doScan将其添加到容器中。查看AutowiredAnnotationBeanPostProcessor#postProcessPropertyValues，其中字符解析器StringValueResolver在PropertyPlaceholderConfigurer中添加到BeanFactory中。
 
+测试：
+```
+@Component
+public class Car {
+
+	@Value("${brand}")
+	private String brand;
+}
+```
+value-annotation.xml
+```
+<?xml version="1.0" encoding="UTF-8"?>
+<beans xmlns="http://www.springframework.org/schema/beans"
+       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+       xmlns:context="http://www.springframework.org/schema/context"
+       xsi:schemaLocation="http://www.springframework.org/schema/beans
+	         http://www.springframework.org/schema/beans/spring-beans.xsd
+		 http://www.springframework.org/schema/context
+		 http://www.springframework.org/schema/context/spring-context-4.0.xsd">
+
+    <bean class="org.springframework.beans.factory.PropertyPlaceholderConfigurer">
+        <property name="location" value="classpath:car.properties" />
+    </bean>
 
+    <context:component-scan base-package="org.springframework.test.bean"/>
 
+</beans>
+```
+car.properties
+```
+brand=lamborghini
+```
+```
+public class ValueAnnotationTest {
+
+	@Test
+	public void testValueAnnotation() throws Exception {
+		ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext("classpath:value-annotation.xml");
+
+		Car car = applicationContext.getBean("car", Car.class);
+		assertThat(car.getBrand()).isEqualTo("lamborghini");
+	}
+}
+
+```
 
 
 

src/main/java/org/springframework/aop/framework/autoproxy/DefaultAdvisorAutoProxyCreator.java

@@ -6,6 +6,7 @@
 import org.springframework.aop.aspectj.AspectJExpressionPointcutAdvisor;
 import org.springframework.aop.framework.ProxyFactory;
 import org.springframework.beans.BeansException;
+import org.springframework.beans.PropertyValues;
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.BeanFactoryAware;
 import org.springframework.beans.factory.config.BeanDefinition;
@@ -73,4 +74,9 @@ public Object postProcessBeforeInitialization(Object bean, String beanName) thro
 	public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
 		return bean;
 	}
+
+	@Override
+	public PropertyValues postProcessPropertyValues(PropertyValues pvs, Object bean, String beanName) throws BeansException {
+		return pvs;
+	}
 }

src/main/java/org/springframework/beans/factory/PropertyPlaceholderConfigurer.java

@@ -7,6 +7,7 @@
 import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
 import org.springframework.core.io.DefaultResourceLoader;
 import org.springframework.core.io.Resource;
+import org.springframework.util.StringValueResolver;
 
 import java.io.IOException;
 import java.util.Properties;
@@ -30,6 +31,10 @@ public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory)
 
 		//属性值替换占位符
 		processProperties(beanFactory, properties);
+
+		//往容器中添加字符解析器，供解析@Value注解使用
+		StringValueResolver valueResolver = new PlaceholderResolvingStringValueResolver(properties);
+		beanFactory.addEmbeddedValueResolver(valueResolver);
 	}
 
 	/**
@@ -69,22 +74,40 @@ private void resolvePropertyValues(BeanDefinition beanDefinition, Properties pro
 		for (PropertyValue propertyValue : propertyValues.getPropertyValues()) {
 			Object value = propertyValue.getValue();
 			if (value instanceof String) {
-				//TODO 仅简单支持一个占位符的格式
-				String strVal = (String) value;
-				StringBuffer buf = new StringBuffer(strVal);
-				int startIndex = strVal.indexOf(PLACEHOLDER_PREFIX);
-				int endIndex = strVal.indexOf(PLACEHOLDER_SUFFIX);
-				if (startIndex != -1 && endIndex != -1 && startIndex < endIndex) {
-					String propKey = strVal.substring(startIndex + 2, endIndex);
-					String propVal = properties.getProperty(propKey);
-					buf.replace(startIndex, endIndex + 1, propVal);
-					propertyValues.addPropertyValue(new PropertyValue(propertyValue.getName(), buf.toString()));
-				}
+				value = resolvePlaceholder((String) value, properties);
+				propertyValues.addPropertyValue(new PropertyValue(propertyValue.getName(), value));
 			}
 		}
 	}
 
+	private String resolvePlaceholder(String value, Properties properties) {
+		//TODO 仅简单支持一个占位符的格式
+		String strVal = value;
+		StringBuffer buf = new StringBuffer(strVal);
+		int startIndex = strVal.indexOf(PLACEHOLDER_PREFIX);
+		int endIndex = strVal.indexOf(PLACEHOLDER_SUFFIX);
+		if (startIndex != -1 && endIndex != -1 && startIndex < endIndex) {
+			String propKey = strVal.substring(startIndex + 2, endIndex);
+			String propVal = properties.getProperty(propKey);
+			buf.replace(startIndex, endIndex + 1, propVal);
+		}
+		return buf.toString();
+	}
+
 	public void setLocation(String location) {
 		this.location = location;
 	}
+
+	private class PlaceholderResolvingStringValueResolver implements StringValueResolver {
+
+		private final Properties properties;
+
+		public PlaceholderResolvingStringValueResolver(Properties properties) {
+			this.properties = properties;
+		}
+
+		public String resolveStringValue(String strVal) throws BeansException {
+			return PropertyPlaceholderConfigurer.this.resolvePlaceholder(strVal, properties);
+		}
+	}
 }

src/main/java/org/springframework/beans/factory/annotation/AutowiredAnnotationBeanPostProcessor.java

@@ -0,0 +1,61 @@
+package org.springframework.beans.factory.annotation;
+
+import cn.hutool.core.bean.BeanUtil;
+import org.springframework.beans.BeansException;
+import org.springframework.beans.PropertyValues;
+import org.springframework.beans.factory.BeanFactory;
+import org.springframework.beans.factory.BeanFactoryAware;
+import org.springframework.beans.factory.ConfigurableListableBeanFactory;
+import org.springframework.beans.factory.config.InstantiationAwareBeanPostProcessor;
+
+import java.lang.reflect.Field;
+
+/**
+ * 处理@Autowired和@Value注解的BeanPostProcessor
+ *
+ * @author derekyi
+ * @date 2020/12/27
+ */
+public class AutowiredAnnotationBeanPostProcessor implements InstantiationAwareBeanPostProcessor, BeanFactoryAware {
+
+	private ConfigurableListableBeanFactory beanFactory;
+
+	@Override
+	public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
+		this.beanFactory = (ConfigurableListableBeanFactory) beanFactory;
+	}
+
+	@Override
+	public PropertyValues postProcessPropertyValues(PropertyValues pvs, Object bean, String beanName) throws BeansException {
+		//处理@Value注解
+		Class<?> clazz = bean.getClass();
+		Field[] fields = clazz.getDeclaredFields();
+		for (Field field : fields) {
+			Value valueAnnotation = field.getAnnotation(Value.class);
+			if (valueAnnotation != null) {
+				String value = valueAnnotation.value();
+				value = beanFactory.resolveEmbeddedValue(value);
+				BeanUtil.setFieldValue(bean, field.getName(), value);
+			}
+		}
+
+		//处理@Autowired注解（下一节实现）
+
+		return pvs;
+	}
+
+	@Override
+	public Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) throws BeansException {
+		return null;
+	}
+
+	@Override
+	public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
+		return null;
+	}
+
+	@Override
+	public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
+		return null;
+	}
+}

src/main/java/org/springframework/beans/factory/annotation/Value.java

@@ -0,0 +1,17 @@
+package org.springframework.beans.factory.annotation;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * @author derekyi
+ * @date 2020/12/27
+ */
+@Retention(RetentionPolicy.RUNTIME)
+@Target({ElementType.FIELD, ElementType.METHOD, ElementType.PARAMETER})
+public @interface Value {
+
+	String value();
+}

src/main/java/org/springframework/beans/factory/config/ConfigurableBeanFactory.java

@@ -1,6 +1,7 @@
 package org.springframework.beans.factory.config;
 
 import org.springframework.beans.factory.HierarchicalBeanFactory;
+import org.springframework.util.StringValueResolver;
 
 /**
  * @author derekyi
@@ -17,4 +18,8 @@ public interface ConfigurableBeanFactory extends HierarchicalBeanFactory, Single
 	 * 销毁单例bean
 	 */
 	void destroySingletons();
+
+	void addEmbeddedValueResolver(StringValueResolver valueResolver);
+
+	String resolveEmbeddedValue(String value);
 }

src/main/java/org/springframework/beans/factory/config/InstantiationAwareBeanPostProcessor.java

@@ -1,6 +1,7 @@
 package org.springframework.beans.factory.config;
 
 import org.springframework.beans.BeansException;
+import org.springframework.beans.PropertyValues;
 
 /**
  * @author derekyi
@@ -17,4 +18,16 @@ public interface InstantiationAwareBeanPostProcessor extends BeanPostProcessor {
 	 * @throws BeansException
 	 */
 	Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) throws BeansException;
+
+	/**
+	 * bean实例化之后，设置属性之前执行
+	 *
+	 * @param pvs
+	 * @param bean
+	 * @param beanName
+	 * @return
+	 * @throws BeansException
+	 */
+	PropertyValues postProcessPropertyValues(PropertyValues pvs, Object bean, String beanName)
+			throws BeansException;
 }

src/main/java/org/springframework/beans/factory/support/AbstractAutowireCapableBeanFactory.java

@@ -5,6 +5,7 @@
 import cn.hutool.core.util.StrUtil;
 import org.springframework.beans.BeansException;
 import org.springframework.beans.PropertyValue;
+import org.springframework.beans.PropertyValues;
 import org.springframework.beans.factory.BeanFactoryAware;
 import org.springframework.beans.factory.DisposableBean;
 import org.springframework.beans.factory.InitializingBean;
@@ -64,6 +65,8 @@ protected Object doCreateBean(String beanName, BeanDefinition beanDefinition) {
 		Object bean = null;
 		try {
 			bean = createBeanInstance(beanDefinition);
+			//在设置bean属性之前，允许BeanPostProcessor修改属性值
+			applyBeanPostprocessorsBeforeApplyingPropertyValues(beanName, bean, beanDefinition);
 			//为bean填充属性
 			applyPropertyValues(beanName, bean, beanDefinition);
 			//执行bean的初始化方法和BeanPostProcessor的前置和后置处理方法
@@ -81,6 +84,26 @@ protected Object doCreateBean(String beanName, BeanDefinition beanDefinition) {
 		return bean;
 	}
 
+	/**
+	 * 在设置bean属性之前，允许BeanPostProcessor修改属性值
+	 *
+	 * @param beanName
+	 * @param bean
+	 * @param beanDefinition
+	 */
+	protected void applyBeanPostprocessorsBeforeApplyingPropertyValues(String beanName, Object bean, BeanDefinition beanDefinition) {
+		for (BeanPostProcessor beanPostProcessor : getBeanPostProcessors()) {
+			if (beanPostProcessor instanceof InstantiationAwareBeanPostProcessor) {
+				PropertyValues pvs = ((InstantiationAwareBeanPostProcessor) beanPostProcessor).postProcessPropertyValues(beanDefinition.getPropertyValues(), bean, beanName);
+				if (pvs != null) {
+					for (PropertyValue propertyValue : pvs.getPropertyValues()) {
+						beanDefinition.getPropertyValues().addPropertyValue(propertyValue);
+					}
+				}
+			}
+		}
+	}
+
 	/**
 	 * 注册有销毁方法的bean，即bean继承自DisposableBean或有自定义的销毁方法
 	 *

src/main/java/org/springframework/beans/factory/support/AbstractBeanFactory.java

@@ -1,18 +1,16 @@
 package org.springframework.beans.factory.support;
 
-import cn.hutool.core.lang.Assert;
 import org.springframework.beans.BeansException;
-import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.FactoryBean;
 import org.springframework.beans.factory.config.BeanDefinition;
 import org.springframework.beans.factory.config.BeanPostProcessor;
 import org.springframework.beans.factory.config.ConfigurableBeanFactory;
+import org.springframework.util.StringValueResolver;
 
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
-import java.util.concurrent.CopyOnWriteArrayList;
 
 /**
  * @author derekyi
@@ -24,6 +22,8 @@ public abstract class AbstractBeanFactory extends DefaultSingletonBeanRegistry i
 
 	private final Map<String, Object> factoryBeanObjectCache = new HashMap<>();
 
+	private final List<StringValueResolver> embeddedValueResolvers = new ArrayList<StringValueResolver>();
+
 	@Override
 	public Object getBean(String name) throws BeansException {
 		Object sharedInstance = getSingleton(name);
@@ -87,4 +87,16 @@ public void addBeanPostProcessor(BeanPostProcessor beanPostProcessor) {
 	public List<BeanPostProcessor> getBeanPostProcessors() {
 		return this.beanPostProcessors;
 	}
+
+	public void addEmbeddedValueResolver(StringValueResolver valueResolver) {
+		this.embeddedValueResolvers.add(valueResolver);
+	}
+
+	public String resolveEmbeddedValue(String value) {
+		String result = value;
+		for (StringValueResolver resolver : this.embeddedValueResolvers) {
+			result = resolver.resolveStringValue(result);
+		}
+		return result;
+	}
 }