此版本仍在开发中，尚未被视为稳定版本。对于最新的稳定版本，请使用 Spring Framework 6.2.4！spring-doc.cadn.net.cn

XML 架构创作

从 2.0 版本开始， Spring 具有一种将基于 schema 的扩展添加到 用于定义和配置 bean 的基本 Spring XML 格式。本节涵盖 如何编写自己的自定义 XML bean 定义解析器，以及 将此类解析器集成到 Spring IoC 容器中。spring-doc.cadn.net.cn

为了便于编写使用架构感知 XML 编辑器的配置文件， Spring 的可扩展 XML 配置机制基于 XML Schema。如果你不是 熟悉 Spring 标准附带的当前 XML 配置扩展 Spring 发行版，您应该首先阅读上一节 XML 模式。spring-doc.cadn.net.cn

要创建新的 XML 配置扩展：spring-doc.cadn.net.cn

  1. 创作 XML 架构以描述您的自定义元素。spring-doc.cadn.net.cn

  2. 编写自定义代码NamespaceHandler实现。spring-doc.cadn.net.cn

  3. 对一个或多个进行编码BeanDefinitionParser实现 （这是完成真正工作的地方）。spring-doc.cadn.net.cn

  4. 在 Spring 中注册您的新工件。spring-doc.cadn.net.cn

对于一个统一的示例，我们创建一个 XML 扩展名（自定义 XML 元素），允许我们配置以下类型的对象SimpleDateFormat（来自java.text包）。当我们完成时， 我们将能够定义 bean 类型的定义SimpleDateFormat如下：spring-doc.cadn.net.cn

<myns:dateformat id="dateFormat"
	pattern="yyyy-MM-dd HH:mm"
	lenient="true"/>

（我们包括更详细的 示例将在本附录的后面部分进行。第一个简单示例的目的是引导您 通过创建自定义扩展的基本步骤。spring-doc.cadn.net.cn

编写架构

创建用于 Spring 的 IoC 容器的 XML 配置扩展的开头为 编写 XML 架构来描述扩展。在我们的示例中，我们使用以下架构 配置SimpleDateFormat对象：spring-doc.cadn.net.cn

<!-- myns.xsd (inside package org/springframework/samples/xml) -->

<?xml version="1.0" encoding="UTF-8"?>
<xsd:schema xmlns="http://www.mycompany.example/schema/myns"
		xmlns:xsd="http://www.w3.org/2001/XMLSchema"
		xmlns:beans="http://www.springframework.org/schema/beans"
		targetNamespace="http://www.mycompany.example/schema/myns"
		elementFormDefault="qualified"
		attributeFormDefault="unqualified">

	<xsd:import namespace="http://www.springframework.org/schema/beans"/>

	<xsd:element name="dateformat">
		<xsd:complexType>
			<xsd:complexContent>
				<xsd:extension base="beans:identifiedType"> (1)
					<xsd:attribute name="lenient" type="xsd:boolean"/>
					<xsd:attribute name="pattern" type="xsd:string" use="required"/>
				</xsd:extension>
			</xsd:complexContent>
		</xsd:complexType>
	</xsd:element>
</xsd:schema>
1 指示的行包含所有可识别标记的扩展基础 （意味着他们有一个id属性，我们可以将其用作 容器）。我们可以使用这个属性，因为我们导入了 Spring 提供的beansNamespace。

前面的 schema 允许我们配置SimpleDateFormat对象直接放在 XML 应用程序上下文文件<myns:dateformat/>元素，如下所示 示例显示：spring-doc.cadn.net.cn

<myns:dateformat id="dateFormat"
	pattern="yyyy-MM-dd HH:mm"
	lenient="true"/>

请注意，在我们创建了基础结构类之后，前面的 XML 代码片段是 与以下 XML 代码片段基本相同：spring-doc.cadn.net.cn

<bean id="dateFormat" class="java.text.SimpleDateFormat">
	<constructor-arg value="yyyy-MM-dd HH:mm"/>
	<property name="lenient" value="true"/>
</bean>

前面两个代码片段中的第二个 在容器中创建一个 Bean（由名称dateFormat的类型SimpleDateFormat） 设置了几个属性。spring-doc.cadn.net.cn

基于 schema 的创建配置格式的方法允许紧密集成 使用具有架构感知 XML 编辑器的 IDE。通过使用正确编写的架构，您可以 可以使用自动完成让用户在多个配置选项之间进行选择 在枚举中定义。

编码NamespaceHandler

除了 schema 之外，我们还需要一个NamespaceHandler解析 Spring 在解析配置文件时遇到的这个特定名称空间。在此示例中，NamespaceHandler应该负责解析myns:dateformat元素。spring-doc.cadn.net.cn

这NamespaceHandler界面有三种方法：spring-doc.cadn.net.cn

  • init()：允许初始化NamespaceHandler，由 Spring 之前。spring-doc.cadn.net.cn

  • BeanDefinition parse(Element, ParserContext)：当 Spring 遇到 顶级元素（不嵌套在 bean 定义或其他命名空间中）。 此方法本身可以注册 Bean 定义，返回 Bean 定义，或同时返回两者。spring-doc.cadn.net.cn

  • BeanDefinitionHolder decorate(Node, BeanDefinitionHolder, ParserContext)：叫 当 Spring 遇到不同命名空间的属性或嵌套元素时。 一个或多个 bean 定义的装饰（例如）与 Spring 支持的范围一起使用。 我们首先突出显示一个简单的示例，不使用装饰，然后 我们在一个更高级的例子中展示 Decoration。spring-doc.cadn.net.cn

虽然您可以编写自己的代码NamespaceHandler对于整个 命名空间（因此提供解析命名空间中每个元素的代码）， 通常情况下，Spring XML 配置文件中的每个顶级 XML 元素 结果会得到一个 bean 定义（就像我们的例子中一样，其中单个<myns:dateformat/>元素会生成单个SimpleDateFormatbean 定义）。Spring 具有 支持此方案的便利类的数量。在下面的示例中，我们 使用NamespaceHandlerSupport类：spring-doc.cadn.net.cn

package org.springframework.samples.xml;

import org.springframework.beans.factory.xml.NamespaceHandlerSupport;

public class MyNamespaceHandler extends NamespaceHandlerSupport {

	public void init() {
		registerBeanDefinitionParser("dateformat", new SimpleDateFormatBeanDefinitionParser());
	}
}
package org.springframework.samples.xml

import org.springframework.beans.factory.xml.NamespaceHandlerSupport

class MyNamespaceHandler : NamespaceHandlerSupport {

	override fun init() {
		registerBeanDefinitionParser("dateformat", SimpleDateFormatBeanDefinitionParser())
	}
}

You may notice that there is not actually a whole lot of parsing logic in this class. Indeed, the NamespaceHandlerSupport class has a built-in notion of delegation. It supports the registration of any number of BeanDefinitionParser instances, to which it delegates to when it needs to parse an element in its namespace. This clean separation of concerns lets a NamespaceHandler handle the orchestration of the parsing of all of the custom elements in its namespace while delegating to BeanDefinitionParsers to do the grunt work of the XML parsing. This means that each BeanDefinitionParser contains only the logic for parsing a single custom element, as we can see in the next step.spring-doc.cadn.net.cn

Using BeanDefinitionParser

A BeanDefinitionParser is used if the NamespaceHandler encounters an XML element of the type that has been mapped to the specific bean definition parser (dateformat in this case). In other words, the BeanDefinitionParser is responsible for parsing one distinct top-level XML element defined in the schema. In the parser, we' have access to the XML element (and thus to its subelements, too) so that we can parse our custom XML content, as you can see in the following example:spring-doc.cadn.net.cn

package org.springframework.samples.xml;

import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.xml.AbstractSingleBeanDefinitionParser;
import org.springframework.util.StringUtils;
import org.w3c.dom.Element;

import java.text.SimpleDateFormat;

public class SimpleDateFormatBeanDefinitionParser extends AbstractSingleBeanDefinitionParser { (1)

	protected Class getBeanClass(Element element) {
		return SimpleDateFormat.class; (2)
	}

	protected void doParse(Element element, BeanDefinitionBuilder bean) {
		// this will never be null since the schema explicitly requires that a value be supplied
		String pattern = element.getAttribute("pattern");
		bean.addConstructorArgValue(pattern);

		// this however is an optional property
		String lenient = element.getAttribute("lenient");
		if (StringUtils.hasText(lenient)) {
			bean.addPropertyValue("lenient", Boolean.valueOf(lenient));
		}
	}

}
1 We use the Spring-provided AbstractSingleBeanDefinitionParser to handle a lot of the basic grunt work of creating a single BeanDefinition.
2 We supply the AbstractSingleBeanDefinitionParser superclass with the type that our single BeanDefinition represents. 
package org.springframework.samples.xml

import org.springframework.beans.factory.support.BeanDefinitionBuilder
import org.springframework.beans.factory.xml.AbstractSingleBeanDefinitionParser
import org.springframework.util.StringUtils
import org.w3c.dom.Element

import java.text.SimpleDateFormat

class SimpleDateFormatBeanDefinitionParser : AbstractSingleBeanDefinitionParser() { (1)

	override fun getBeanClass(element: Element): Class<*>? { (2)
		return SimpleDateFormat::class.java
	}

	override fun doParse(element: Element, bean: BeanDefinitionBuilder) {
		// this will never be null since the schema explicitly requires that a value be supplied
		val pattern = element.getAttribute("pattern")
		bean.addConstructorArgValue(pattern)

		// this however is an optional property
		val lenient = element.getAttribute("lenient")
		if (StringUtils.hasText(lenient)) {
			bean.addPropertyValue("lenient", java.lang.Boolean.valueOf(lenient))
		}
	}
}
1 We use the Spring-provided AbstractSingleBeanDefinitionParser to handle a lot of the basic grunt work of creating a single BeanDefinition.
2 We supply the AbstractSingleBeanDefinitionParser superclass with the type that our single BeanDefinition represents.

In this simple case, this is all that we need to do. The creation of our single BeanDefinition is handled by the AbstractSingleBeanDefinitionParser superclass, as is the extraction and setting of the bean definition’s unique identifier.spring-doc.cadn.net.cn

Registering the Handler and the Schema

The coding is finished. All that remains to be done is to make the Spring XML parsing infrastructure aware of our custom element. We do so by registering our custom namespaceHandler and custom XSD file in two special-purpose properties files. These properties files are both placed in a META-INF directory in your application and can, for example, be distributed alongside your binary classes in a JAR file. The Spring XML parsing infrastructure automatically picks up your new extension by consuming these special properties files, the formats of which are detailed in the next two sections.spring-doc.cadn.net.cn

Writing META-INF/spring.handlers

The properties file called spring.handlers contains a mapping of XML Schema URIs to namespace handler classes. For our example, we need to write the following:spring-doc.cadn.net.cn

http\://www.mycompany.example/schema/myns=org.springframework.samples.xml.MyNamespaceHandler

(The : character is a valid delimiter in the Java properties format, so : character in the URI needs to be escaped with a backslash.)spring-doc.cadn.net.cn

The first part (the key) of the key-value pair is the URI associated with your custom namespace extension and needs to exactly match exactly the value of the targetNamespace attribute, as specified in your custom XSD schema.spring-doc.cadn.net.cn

Writing 'META-INF/spring.schemas'

The properties file called spring.schemas contains a mapping of XML Schema locations (referred to, along with the schema declaration, in XML files that use the schema as part of the xsi:schemaLocation attribute) to classpath resources. This file is needed to prevent Spring from absolutely having to use a default EntityResolver that requires Internet access to retrieve the schema file. If you specify the mapping in this properties file, Spring searches for the schema (in this case, myns.xsd in the org.springframework.samples.xml package) on the classpath. The following snippet shows the line we need to add for our custom schema:spring-doc.cadn.net.cn

http\://www.mycompany.example/schema/myns/myns.xsd=org/springframework/samples/xml/myns.xsd

(Remember that the : character must be escaped.)spring-doc.cadn.net.cn

You are encouraged to deploy your XSD file (or files) right alongside the NamespaceHandler and BeanDefinitionParser classes on the classpath.spring-doc.cadn.net.cn

Using a Custom Extension in Your Spring XML Configuration

Using a custom extension that you yourself have implemented is no different from using one of the “custom” extensions that Spring provides. The following example uses the custom <dateformat/> element developed in the previous steps in a Spring XML configuration file:spring-doc.cadn.net.cn

<?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:myns="http://www.mycompany.example/schema/myns"
	xsi:schemaLocation="
		http://www.springframework.org/schema/beans https://www.springframework.org/schema/beans/spring-beans.xsd
		http://www.mycompany.example/schema/myns http://www.mycompany.com/schema/myns/myns.xsd">

	<!-- as a top-level bean -->
	<myns:dateformat id="defaultDateFormat" pattern="yyyy-MM-dd HH:mm" lenient="true"/> (1)

	<bean id="jobDetailTemplate" abstract="true">
		<property name="dateFormat">
			<!-- as an inner bean -->
			<myns:dateformat pattern="HH:mm MM-dd-yyyy"/>
		</property>
	</bean>

</beans>
1 Our custom bean.

More Detailed Examples

This section presents some more detailed examples of custom XML extensions.spring-doc.cadn.net.cn

Nesting Custom Elements within Custom Elements

The example presented in this section shows how you to write the various artifacts required to satisfy a target of the following configuration:spring-doc.cadn.net.cn

<?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:foo="http://www.foo.example/schema/component"
	xsi:schemaLocation="
		http://www.springframework.org/schema/beans https://www.springframework.org/schema/beans/spring-beans.xsd
		http://www.foo.example/schema/component http://www.foo.example/schema/component/component.xsd">

	<foo:component id="bionic-family" name="Bionic-1">
		<foo:component name="Mother-1">
			<foo:component name="Karate-1"/>
			<foo:component name="Sport-1"/>
		</foo:component>
		<foo:component name="Rock-1"/>
	</foo:component>

</beans>

The preceding configuration nests custom extensions within each other. The class that is actually configured by the <foo:component/> element is the Component class (shown in the next example). Notice how the Component class does not expose a setter method for the components property. This makes it hard (or rather impossible) to configure a bean definition for the Component class by using setter injection. The following listing shows the Component class:spring-doc.cadn.net.cn

package com.foo;

import java.util.ArrayList;
import java.util.List;

public class Component {

	private String name;
	private List<Component> components = new ArrayList<Component> ();

	// there is no setter method for the 'components'
	public void addComponent(Component component) {
		this.components.add(component);
	}

	public List<Component> getComponents() {
		return components;
	}

	public String getName() {
		return name;
	}

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

import java.util.ArrayList

class Component {

	var name: String? = null
	private val components = ArrayList<Component>()

	// there is no setter method for the 'components'
	fun addComponent(component: Component) {
		this.components.add(component)
	}

	fun getComponents(): List<Component> {
		return components
	}
}

The typical solution to this issue is to create a custom FactoryBean that exposes a setter property for the components property. The following listing shows such a custom FactoryBean:spring-doc.cadn.net.cn

package com.foo;

import org.springframework.beans.factory.FactoryBean;

import java.util.List;

public class ComponentFactoryBean implements FactoryBean<Component> {

	private Component parent;
	private List<Component> children;

	public void setParent(Component parent) {
		this.parent = parent;
	}

	public void setChildren(List<Component> children) {
		this.children = children;
	}

	public Component getObject() throws Exception {
		if (this.children != null && this.children.size() > 0) {
			for (Component child : children) {
				this.parent.addComponent(child);
			}
		}
		return this.parent;
	}

	public Class<Component> getObjectType() {
		return Component.class;
	}

	public boolean isSingleton() {
		return true;
	}
}
package com.foo

import org.springframework.beans.factory.FactoryBean
import org.springframework.stereotype.Component

class ComponentFactoryBean : FactoryBean<Component> {

	private var parent: Component? = null
	private var children: List<Component>? = null

	fun setParent(parent: Component) {
		this.parent = parent
	}

	fun setChildren(children: List<Component>) {
		this.children = children
	}

	override fun getObject(): Component? {
		if (this.children != null && this.children!!.isNotEmpty()) {
			for (child in children!!) {
				this.parent!!.addComponent(child)
			}
		}
		return this.parent
	}

	override fun getObjectType(): Class<Component>? {
		return Component::class.java
	}

	override fun isSingleton(): Boolean {
		return true
	}
}

This works nicely, but it exposes a lot of Spring plumbing to the end user. What we are going to do is write a custom extension that hides away all of this Spring plumbing. If we stick to the steps described previously, we start off by creating the XSD schema to define the structure of our custom tag, as the following listing shows:spring-doc.cadn.net.cn

<?xml version="1.0" encoding="UTF-8" standalone="no"?>

<xsd:schema xmlns="http://www.foo.example/schema/component"
		xmlns:xsd="http://www.w3.org/2001/XMLSchema"
		targetNamespace="http://www.foo.example/schema/component"
		elementFormDefault="qualified"
		attributeFormDefault="unqualified">

	<xsd:element name="component">
		<xsd:complexType>
			<xsd:choice minOccurs="0" maxOccurs="unbounded">
				<xsd:element ref="component"/>
			</xsd:choice>
			<xsd:attribute name="id" type="xsd:ID"/>
			<xsd:attribute name="name" use="required" type="xsd:string"/>
		</xsd:complexType>
	</xsd:element>

</xsd:schema>

Again following the process described earlier, we then create a custom NamespaceHandler:spring-doc.cadn.net.cn

package com.foo;

import org.springframework.beans.factory.xml.NamespaceHandlerSupport;

public class ComponentNamespaceHandler extends NamespaceHandlerSupport {

	public void init() {
		registerBeanDefinitionParser("component", new ComponentBeanDefinitionParser());
	}
}
package com.foo

import org.springframework.beans.factory.xml.NamespaceHandlerSupport

class ComponentNamespaceHandler : NamespaceHandlerSupport() {

	override fun init() {
		registerBeanDefinitionParser("component", ComponentBeanDefinitionParser())
	}
}

Next up is the custom BeanDefinitionParser. Remember that we are creating a BeanDefinition that describes a ComponentFactoryBean. The following listing shows our custom BeanDefinitionParser implementation:spring-doc.cadn.net.cn

package com.foo;

import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.support.AbstractBeanDefinition;
import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.support.ManagedList;
import org.springframework.beans.factory.xml.AbstractBeanDefinitionParser;
import org.springframework.beans.factory.xml.ParserContext;
import org.springframework.util.xml.DomUtils;
import org.w3c.dom.Element;

import java.util.List;

public class ComponentBeanDefinitionParser extends AbstractBeanDefinitionParser {

	protected AbstractBeanDefinition parseInternal(Element element, ParserContext parserContext) {
		return parseComponentElement(element);
	}

	private static AbstractBeanDefinition parseComponentElement(Element element) {
		BeanDefinitionBuilder factory = BeanDefinitionBuilder.rootBeanDefinition(ComponentFactoryBean.class);
		factory.addPropertyValue("parent", parseComponent(element));

		List<Element> childElements = DomUtils.getChildElementsByTagName(element, "component");
		if (childElements != null && childElements.size() > 0) {
			parseChildComponents(childElements, factory);
		}

		return factory.getBeanDefinition();
	}

	private static BeanDefinition parseComponent(Element element) {
		BeanDefinitionBuilder component = BeanDefinitionBuilder.rootBeanDefinition(Component.class);
		component.addPropertyValue("name", element.getAttribute("name"));
		return component.getBeanDefinition();
	}

	private static void parseChildComponents(List<Element> childElements, BeanDefinitionBuilder factory) {
		ManagedList<BeanDefinition> children = new ManagedList<>(childElements.size());
		for (Element element : childElements) {
			children.add(parseComponentElement(element));
		}
		factory.addPropertyValue("children", children);
	}
}
package com.foo

import org.springframework.beans.factory.config.BeanDefinition
import org.springframework.beans.factory.support.AbstractBeanDefinition
import org.springframework.beans.factory.support.BeanDefinitionBuilder
import org.springframework.beans.factory.support.ManagedList
import org.springframework.beans.factory.xml.AbstractBeanDefinitionParser
import org.springframework.beans.factory.xml.ParserContext
import org.springframework.util.xml.DomUtils
import org.w3c.dom.Element

import java.util.List

class ComponentBeanDefinitionParser : AbstractBeanDefinitionParser() {

	override fun parseInternal(element: Element, parserContext: ParserContext): AbstractBeanDefinition? {
		return parseComponentElement(element)
	}

	private fun parseComponentElement(element: Element): AbstractBeanDefinition {
		val factory = BeanDefinitionBuilder.rootBeanDefinition(ComponentFactoryBean::class.java)
		factory.addPropertyValue("parent", parseComponent(element))

		val childElements = DomUtils.getChildElementsByTagName(element, "component")
		if (childElements != null && childElements.size > 0) {
			parseChildComponents(childElements, factory)
		}

		return factory.getBeanDefinition()
	}

	private fun parseComponent(element: Element): BeanDefinition {
		val component = BeanDefinitionBuilder.rootBeanDefinition(Component::class.java)
		component.addPropertyValue("name", element.getAttribute("name"))
		return component.beanDefinition
	}

	private fun parseChildComponents(childElements: List<Element>, factory: BeanDefinitionBuilder) {
		val children = ManagedList<BeanDefinition>(childElements.size)
		for (element in childElements) {
			children.add(parseComponentElement(element))
		}
		factory.addPropertyValue("children", children)
	}
}

Finally, the various artifacts need to be registered with the Spring XML infrastructure, by modifying the META-INF/spring.handlers and META-INF/spring.schemas files, as follows:spring-doc.cadn.net.cn

# in 'META-INF/spring.handlers'
http\://www.foo.example/schema/component=com.foo.ComponentNamespaceHandler
# in 'META-INF/spring.schemas'
http\://www.foo.example/schema/component/component.xsd=com/foo/component.xsd

Custom Attributes on “Normal” Elements

Writing your own custom parser and the associated artifacts is not hard. However, it is sometimes not the right thing to do. Consider a scenario where you need to add metadata to already existing bean definitions. In this case, you certainly do not want to have to write your own entire custom extension. Rather, you merely want to add an additional attribute to the existing bean definition element.spring-doc.cadn.net.cn

By way of another example, suppose that you define a bean definition for a service object that (unknown to it) accesses a clustered JCache, and you want to ensure that the named JCache instance is eagerly started within the surrounding cluster. The following listing shows such a definition:spring-doc.cadn.net.cn

<bean id="checkingAccountService" class="com.foo.DefaultCheckingAccountService"
		jcache:cache-name="checking.account">
	<!-- other dependencies here... -->
</bean>

We can then create another BeanDefinition when the 'jcache:cache-name' attribute is parsed. This BeanDefinition then initializes the named JCache for us. We can also modify the existing BeanDefinition for the 'checkingAccountService' so that it has a dependency on this new JCache-initializing BeanDefinition. The following listing shows our JCacheInitializer:spring-doc.cadn.net.cn

package com.foo;

public class JCacheInitializer {

	private final String name;

	public JCacheInitializer(String name) {
		this.name = name;
	}

	public void initialize() {
		// lots of JCache API calls to initialize the named cache...
	}
}
package com.foo

class JCacheInitializer(private val name: String) {

	fun initialize() {
		// lots of JCache API calls to initialize the named cache...
	}
}

Now we can move onto the custom extension. First, we need to author the XSD schema that describes the custom attribute, as follows:spring-doc.cadn.net.cn

<?xml version="1.0" encoding="UTF-8" standalone="no"?>

<xsd:schema xmlns="http://www.foo.example/schema/jcache"
		xmlns:xsd="http://www.w3.org/2001/XMLSchema"
		targetNamespace="http://www.foo.example/schema/jcache"
		elementFormDefault="qualified">

	<xsd:attribute name="cache-name" type="xsd:string"/>

</xsd:schema>

Next, we need to create the associated NamespaceHandler, as follows:spring-doc.cadn.net.cn

package com.foo;

import org.springframework.beans.factory.xml.NamespaceHandlerSupport;

public class JCacheNamespaceHandler extends NamespaceHandlerSupport {

	public void init() {
		super.registerBeanDefinitionDecoratorForAttribute("cache-name",
			new JCacheInitializingBeanDefinitionDecorator());
	}

}
package com.foo

import org.springframework.beans.factory.xml.NamespaceHandlerSupport

class JCacheNamespaceHandler : NamespaceHandlerSupport() {

	override fun init() {
		super.registerBeanDefinitionDecoratorForAttribute("cache-name",
				JCacheInitializingBeanDefinitionDecorator())
	}

}

Next, we need to create the parser. Note that, in this case, because we are going to parse an XML attribute, we write a BeanDefinitionDecorator rather than a BeanDefinitionParser. The following listing shows our BeanDefinitionDecorator implementation:spring-doc.cadn.net.cn

package com.foo;

import org.springframework.beans.factory.config.BeanDefinitionHolder;
import org.springframework.beans.factory.support.AbstractBeanDefinition;
import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.xml.BeanDefinitionDecorator;
import org.springframework.beans.factory.xml.ParserContext;
import org.w3c.dom.Attr;
import org.w3c.dom.Node;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class JCacheInitializingBeanDefinitionDecorator implements BeanDefinitionDecorator {

	private static final String[] EMPTY_STRING_ARRAY = new String[0];

	public BeanDefinitionHolder decorate(Node source, BeanDefinitionHolder holder,
			ParserContext ctx) {
		String initializerBeanName = registerJCacheInitializer(source, ctx);
		createDependencyOnJCacheInitializer(holder, initializerBeanName);
		return holder;
	}

	private void createDependencyOnJCacheInitializer(BeanDefinitionHolder holder,
			String initializerBeanName) {
		AbstractBeanDefinition definition = ((AbstractBeanDefinition) holder.getBeanDefinition());
		String[] dependsOn = definition.getDependsOn();
		if (dependsOn == null) {
			dependsOn = new String[]{initializerBeanName};
		} else {
			List dependencies = new ArrayList(Arrays.asList(dependsOn));
			dependencies.add(initializerBeanName);
			dependsOn = (String[]) dependencies.toArray(EMPTY_STRING_ARRAY);
		}
		definition.setDependsOn(dependsOn);
	}

	private String registerJCacheInitializer(Node source, ParserContext ctx) {
		String cacheName = ((Attr) source).getValue();
		String beanName = cacheName + "-initializer";
		if (!ctx.getRegistry().containsBeanDefinition(beanName)) {
			BeanDefinitionBuilder initializer = BeanDefinitionBuilder.rootBeanDefinition(JCacheInitializer.class);
			initializer.addConstructorArg(cacheName);
			ctx.getRegistry().registerBeanDefinition(beanName, initializer.getBeanDefinition());
		}
		return beanName;
	}
}
package com.foo

import org.springframework.beans.factory.config.BeanDefinitionHolder
import org.springframework.beans.factory.support.AbstractBeanDefinition
import org.springframework.beans.factory.support.BeanDefinitionBuilder
import org.springframework.beans.factory.xml.BeanDefinitionDecorator
import org.springframework.beans.factory.xml.ParserContext
import org.w3c.dom.Attr
import org.w3c.dom.Node

import java.util.ArrayList

class JCacheInitializingBeanDefinitionDecorator : BeanDefinitionDecorator {

	override fun decorate(source: Node, holder: BeanDefinitionHolder,
						ctx: ParserContext): BeanDefinitionHolder {
		val initializerBeanName = registerJCacheInitializer(source, ctx)
		createDependencyOnJCacheInitializer(holder, initializerBeanName)
		return holder
	}

	private fun createDependencyOnJCacheInitializer(holder: BeanDefinitionHolder,
													initializerBeanName: String) {
		val definition = holder.beanDefinition as AbstractBeanDefinition
		var dependsOn = definition.dependsOn
		dependsOn = if (dependsOn == null) {
			arrayOf(initializerBeanName)
		} else {
			val dependencies = ArrayList(listOf(*dependsOn))
			dependencies.add(initializerBeanName)
			dependencies.toTypedArray()
		}
		definition.setDependsOn(*dependsOn)
	}

	private fun registerJCacheInitializer(source: Node, ctx: ParserContext): String {
		val cacheName = (source as Attr).value
		val beanName = "$cacheName-initializer"
		if (!ctx.registry.containsBeanDefinition(beanName)) {
			val initializer = BeanDefinitionBuilder.rootBeanDefinition(JCacheInitializer::class.java)
			initializer.addConstructorArg(cacheName)
			ctx.registry.registerBeanDefinition(beanName, initializer.getBeanDefinition())
		}
		return beanName
	}
}

Finally, we need to register the various artifacts with the Spring XML infrastructure by modifying the META-INF/spring.handlers and META-INF/spring.schemas files, as follows:spring-doc.cadn.net.cn

# in 'META-INF/spring.handlers'
http\://www.foo.example/schema/jcache=com.foo.JCacheNamespaceHandler
# in 'META-INF/spring.schemas'
http\://www.foo.example/schema/jcache/jcache.xsd=com/foo/jcache.xsd