spring schema扩展

2018-09-05

介绍

Spring 2.5在2.0的基于Schema的Bean配置的基础之上，再增加了扩展XML配置的机制。通过该机制，我们可以编写自己的Schema，并根据自定义的Schema用自定的标签配置Bean。要使用的Spring的扩展XML配置机制，也比较简单，有以下4个步骤：

编写自定义Schema文件；

编写自定义NamespaceHandler；

编写解析BeanDefinition的parser

在Spring中注册上述组建

Maven依赖

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-core</artifactId>
    <version>3.2.4.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-beans</artifactId>
    <version>3.2.4.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-aop</artifactId>
    <version>3.2.4.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-context</artifactId>
    <version>3.2.4.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-context-support</artifactId>
    <version>3.2.4.RELEASE</version>
</dependency>
```      

#### 一、编写schema文件

参考：[http://www.w3school.com.cn/schema/schema_elements_ref.asp](http://www.w3school.com.cn/schema/schema_elements_ref.asp) , 如下`people.xsd`文件:

```xml
<?xml version="1.0" encoding="UTF-8"?>
<xsd:schema xmlns="http://www.pomelo.com/schema/people"
            xmlns:xsd="http://www.w3.org/2001/XMLSchema"
            xmlns:beans="http://www.springframework.org/schema/beans"
            targetNamespace="http://www.pomelo.com/schema/people"
            elementFormDefault="qualified"
            attributeFormDefault="unqualified">
    <xsd:import namespace="http://www.springframework.org/schema/beans"/>

    <xsd:element name="student">
        <xsd:complexType>
            <xsd:complexContent>
                <xsd:extension base="beans:identifiedType">

                    <xsd:attribute name="name" type="xsd:string">
                        <xsd:annotation>
                            <xsd:documentation>姓名</xsd:documentation>
                        </xsd:annotation>
                    </xsd:attribute>

                    <xsd:attribute name="age" type="xsd:string">
                        <xsd:annotation>
                            <xsd:documentation>年龄</xsd:documentation>
                        </xsd:annotation>
                    </xsd:attribute>

                </xsd:extension>
            </xsd:complexContent>
        </xsd:complexType>
    </xsd:element>
</xsd:schema>

二、编写自定义NamespaceHandler

package schema;

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

public class StudentNamespaceHandler extends NamespaceHandlerSupport {

    @Override
    public void init() {
        registerBeanDefinitionParser("student", new StudentBeanDefinitionParser());
    }

}

三、编写BeanDefinition

package schema;

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

public class StudentBeanDefinitionParser extends AbstractSingleBeanDefinitionParser {

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

    protected void doParse(Element element, BeanDefinitionBuilder bean) {
        String name = element.getAttribute("name");
        bean.addPropertyValue("name", name);

        String age = element.getAttribute("age");
        if (StringUtils.hasText(age)) {
            bean.addPropertyValue("age", Integer.valueOf(age));
        }
    }
}

实体类：

package schema;

public class Student {
      
    private String name;  
      
    private int age;  
  
    public String getName() {  
        return name;  
    }  
  
    public void setName(String name) {  
        this.name = name;  
    }  
  
    public int getAge() {  
        return age;  
    }  
  
    public void setAge(int age) {  
        this.age = age;  
    }  
      
}

四、注册schema组件

最后在META-INF目录下添加两个配置文件(spring.handler和spring.schema):

spring.handler配置如下：

1	http\://www.pomelo.com/schema/people=schema.StudentNamespaceHandler

spring.schema配置如下：

1	http\://www.pomelo.com/schema/people.xsd=META-INF/people.xsd

五、测试

新建applicationContext.xml放在clasapath下面：

<?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:people="http://www.pomelo.com/schema/people"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.pomelo.com/schema/people http://www.pomelo.com/schema/people.xsd">

    <people:student id="student1" name="student1" age="18"/>

    <people:student id="student2" name="student2" age="20" />


    <bean id="student3" class="schema.Student">
        <property name="name" value="student3"/>
        <property name="age" value="23"/>
    </bean>

</beans>

java调用：

package schema;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * Created by zhengyong on 17/3/3.
 */
public class SchemaTest {

    public static void main(String[] args) {

        ApplicationContext ctx = new ClassPathXmlApplicationContext("/applicationContext.xml");
        Student student1 = (Student) ctx.getBean("student1");
        Student student2 = (Student) ctx.getBean("student2");
        Student student3 = (Student) ctx.getBean("student3");

        System.out.println("name: " + student1.getName() + " age :" + student1.getAge());
        System.out.println("name: " + student2.getName() + " age :" + student2.getAge());
        System.out.println("name: " + student3.getName() + " age :" + student3.getAge());
    }
}

具体代码详见：https://github.com/zyongjava/pomelo/blob/master/src/main/resources/META-INF/people.xsd