xml文件定义bean

changelog.md

@@ -222,7 +222,57 @@ public class ResourceAndResourceLoaderTest {
 }
 ```
 
+## 在xml文件中定义bean
+> 分支：xml-file-define-bean
 
+有了资源加载器，就可以在xml格式配置文件中声明式地定义bean的信息，资源加载器读取xml文件，解析出bean的信息，自动往容器中注册BeanDefinition。
+
+BeanDefinitionReader是读取bean定义信息的抽象接口，XmlBeanDefinitionReader是从xml文件中读取的实现类。BeanDefinitionReader需要有获取资源的能力，且读取bean定义信息后需要往容器中注册BeanDefinition，因此BeanDefinitionReader的抽象实现类AbstractBeanDefinitionReader拥有ResourceLoader和BeanDefinitionRegistry两个属性。
+
+测试：
+bean定义文件spring.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 id="person" class="org.springframework.test.ioc.bean.Person">
+        <property name="name" value="derek"/>
+        <property name="car" ref="car"/>
+    </bean>
+
+    <bean id="car" class="org.springframework.test.ioc.bean.Car">
+        <property name="brand" value="porsche"/>
+    </bean>
+
+</beans>
+```
+
+```
+public class XmlFileDefineBeanTest {
+
+	@Test
+	public void testXmlFile() throws Exception {
+		DefaultListableBeanFactory beanFactory = new DefaultListableBeanFactory();
+		XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);
+		beanDefinitionReader.loadBeanDefinitions("classpath:spring.xml");
+
+		Person person = (Person) beanFactory.getBean("person");
+		System.out.println(person);
+		assertThat(person.getName()).isEqualTo("derek");
+		assertThat(person.getCar().getBrand()).isEqualTo("porsche");
+
+		Car car = (Car) beanFactory.getBean("car");
+		System.out.println(car);
+		assertThat(car.getBrand()).isEqualTo("porsche");
+	}
+}
+```
 
 
 

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

@@ -0,0 +1,43 @@
+package org.springframework.beans.factory.support;
+
+import org.springframework.beans.BeansException;
+import org.springframework.core.io.DefaultResourceLoader;
+import org.springframework.core.io.Resource;
+import org.springframework.core.io.ResourceLoader;
+
+/**
+ * @author derekyi
+ * @date 2020/11/26
+ */
+public abstract class AbstractBeanDefinitionReader implements BeanDefinitionReader {
+
+	private final BeanDefinitionRegistry registry;
+
+	private ResourceLoader resourceLoader;
+
+	protected AbstractBeanDefinitionReader(BeanDefinitionRegistry registry) {
+		this.registry = registry;
+		this.resourceLoader = new DefaultResourceLoader();
+	}
+
+	@Override
+	public BeanDefinitionRegistry getRegistry() {
+		return registry;
+	}
+
+	@Override
+	public void loadBeanDefinitions(String[] locations) throws BeansException {
+		for (String location : locations) {
+			loadBeanDefinitions(location);
+		}
+	}
+
+	public void setResourceLoader(ResourceLoader resourceLoader) {
+		this.resourceLoader = resourceLoader;
+	}
+
+	@Override
+	public ResourceLoader getResourceLoader() {
+		return resourceLoader;
+	}
+}

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

@@ -0,0 +1,25 @@
+package org.springframework.beans.factory.support;
+
+import cn.hutool.core.bean.BeanException;
+import org.springframework.beans.BeansException;
+import org.springframework.core.io.Resource;
+import org.springframework.core.io.ResourceLoader;
+
+/**
+ * 读取bean定义信息即BeanDefinition的接口
+ *
+ * @author derekyi
+ * @date 2020/11/26
+ */
+public interface BeanDefinitionReader {
+
+	BeanDefinitionRegistry getRegistry();
+
+	ResourceLoader getResourceLoader();
+
+	void loadBeanDefinitions(Resource resource) throws BeansException;
+
+	void loadBeanDefinitions(String location) throws BeansException;
+
+	void loadBeanDefinitions(String[] locations) throws BeansException;
+}

src/main/java/org/springframework/beans/factory/xml/XmlBeanDefinitionReader.java

@@ -0,0 +1,106 @@
+package org.springframework.beans.factory.xml;
+
+import cn.hutool.core.util.StrUtil;
+import cn.hutool.core.util.XmlUtil;
+import org.springframework.beans.BeansException;
+import org.springframework.beans.PropertyValue;
+import org.springframework.beans.factory.config.BeanDefinition;
+import org.springframework.beans.factory.config.BeanReference;
+import org.springframework.beans.factory.support.AbstractBeanDefinitionReader;
+import org.springframework.beans.factory.support.BeanDefinitionRegistry;
+import org.springframework.core.io.Resource;
+import org.springframework.core.io.ResourceLoader;
+import org.w3c.dom.Document;
+import org.w3c.dom.Element;
+import org.w3c.dom.NodeList;
+
+import java.io.InputStream;
+
+/**
+ * 读取配置在xml文件中的bean定义信息
+ *
+ * @author derekyi
+ * @date 2020/11/26
+ */
+public class XmlBeanDefinitionReader extends AbstractBeanDefinitionReader {
+
+	public static final String BEAN_ELEMENT = "bean";
+	public static final String PROPERTY_ELEMENT = "property";
+	public static final String ID_ATTRIBUTE = "id";
+	public static final String NAME_ATTRIBUTE = "name";
+	public static final String CLASS_ATTRIBUTE = "class";
+	public static final String VALUE_ATTRIBUTE = "value";
+	public static final String REF_ATTRIBUTE = "ref";
+
+	public XmlBeanDefinitionReader(BeanDefinitionRegistry registry) {
+		super(registry);
+	}
+
+	@Override
+	public void loadBeanDefinitions(String location) throws BeansException {
+		ResourceLoader resourceLoader = getResourceLoader();
+		Resource resource = resourceLoader.getResource(location);
+		loadBeanDefinitions(resource);
+	}
+
+	@Override
+	public void loadBeanDefinitions(Resource resource) throws BeansException {
+		try {
+			InputStream inputStream = resource.getInputStream();
+			try {
+				doLoadBeanDefinitions(inputStream);
+			} finally {
+				inputStream.close();
+			}
+		} catch (Exception ex) {
+			throw new BeansException("IOException parsing XML document from " + resource, ex);
+		}
+	}
+
+	protected void doLoadBeanDefinitions(InputStream inputStream) throws Exception {
+		Document document = XmlUtil.readXML(inputStream);
+		Element root = document.getDocumentElement();
+		NodeList childNodes = root.getChildNodes();
+		for (int i = 0; i < childNodes.getLength(); i++) {
+			if (childNodes.item(i) instanceof Element) {
+				if (BEAN_ELEMENT.equals(((Element) childNodes.item(i)).getNodeName())) {
+					//解析bean标签
+					Element bean = (Element) childNodes.item(i);
+					String id = bean.getAttribute(ID_ATTRIBUTE);
+					String name = bean.getAttribute(NAME_ATTRIBUTE);
+					String className = bean.getAttribute(CLASS_ATTRIBUTE);
+
+					Class<?> clazz = Class.forName(className);
+					//id优先于name
+					String beanName = StrUtil.isNotEmpty(id) ? id : name;
+					if (StrUtil.isEmpty(beanName)) {
+						//如果id和name都为空，将类名的第一个字母转为小写后作为bean的名称
+						beanName = StrUtil.lowerFirst(clazz.getSimpleName());
+					}
+
+					BeanDefinition beanDefinition = new BeanDefinition(clazz);
+
+					for (int j = 0; j < bean.getChildNodes().getLength(); j++) {
+						if (bean.getChildNodes().item(j) instanceof Element) {
+							if (PROPERTY_ELEMENT.equals(((Element) bean.getChildNodes().item(j)).getNodeName())) {
+								//解析property标签
+								Element property = (Element) bean.getChildNodes().item(j);
+								String nameAttribute = property.getAttribute(NAME_ATTRIBUTE);
+								String valueAttribute = property.getAttribute(VALUE_ATTRIBUTE);
+								String refAttribute = property.getAttribute(REF_ATTRIBUTE);
+
+								Object value = valueAttribute;
+								if (StrUtil.isNotEmpty(refAttribute)) {
+									value = new BeanReference(refAttribute);
+								}
+								PropertyValue propertyValue = new PropertyValue(nameAttribute, value);
+								beanDefinition.getPropertyValues().addPropertyValue(propertyValue);
+							}
+						}
+					}
+					getRegistry().registerBeanDefinition(beanName, beanDefinition);
+				}
+			}
+		}
+	}
+}

src/test/java/org/springframework/test/ioc/XmlFileDefineBeanTest.java

@@ -0,0 +1,32 @@
+package org.springframework.test.ioc;
+
+import org.junit.Test;
+import org.springframework.beans.factory.support.DefaultListableBeanFactory;
+import org.springframework.beans.factory.xml.XmlBeanDefinitionReader;
+import org.springframework.test.ioc.bean.Car;
+import org.springframework.test.ioc.bean.Person;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * @author derekyi
+ * @date 2020/11/26
+ */
+public class XmlFileDefineBeanTest {
+
+	@Test
+	public void testXmlFile() throws Exception {
+		DefaultListableBeanFactory beanFactory = new DefaultListableBeanFactory();
+		XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);
+		beanDefinitionReader.loadBeanDefinitions("classpath:spring.xml");
+
+		Person person = (Person) beanFactory.getBean("person");
+		System.out.println(person);
+		assertThat(person.getName()).isEqualTo("derek");
+		assertThat(person.getCar().getBrand()).isEqualTo("porsche");
+
+		Car car = (Car) beanFactory.getBean("car");
+		System.out.println(car);
+		assertThat(car.getBrand()).isEqualTo("porsche");
+	}
+}

src/test/resources/spring.xml

@@ -0,0 +1,19 @@
+<?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 id="person" class="org.springframework.test.ioc.bean.Person">
+        <property name="name" value="derek"/>
+        <property name="car" ref="car"/>
+    </bean>
+
+    <bean id="car" class="org.springframework.test.ioc.bean.Car">
+        <property name="brand" value="porsche"/>
+    </bean>
+
+</beans>