Spring自定义标签

自定义Spring标签大概分为如下几步：

1. 定义需要扩展的组件
2. 定义xsd文件，描述标签定义
3. 定义 BeanDefinitionParser  用于解析我们的自定义标签
4. 定义 HandlerSupport 用于告诉spring我们自定义的标签通过什么类去解析
5. 定义 spring.schemals和spring.handlers文件

创建扩展的组件

@Data
public class UserDTO {
    private String userName;
    private String email;

}
public class UserExecutor {
    private String userName;
    private String email;
    public UserExecutor(){
    }
    public UserExecutor(UserDTO userDTO) {
        this.userName = userDTO.getUserName();
        this.email = userDTO.getEmail();
    }
    public void init() {
        System.out.println("print user info :" + userName + "___" + email);
    }
    public void des() {
        System.out.println("UserExecutor: destroy");
    }
}

定义xsd文件

定义 BeanDefinitionParser

UserDTO  的 parser

public class UserBeanDefineParser extends AbstractSimpleBeanDefinitionParser {
    static final String USERDTO_CLASS = UserDTO.class.getName();
    @Override
    protected Class getBeanClass(Element element) {
        return UserDTO.class;
    }
    @Override
    protected void doParse(Element element, ParserContext parserContext, BeanDefinitionBuilder builder) {
        String userName = element.getAttribute("userName");
        String email = element.getAttribute("email");
        if (StringUtils.hasText(userName)) {
            builder.addPropertyValue("userName", userName);
        }
        if (StringUtils.hasText(email)) {
            builder.addPropertyValue("email", email);
        }
        super.doParse(element, parserContext, builder);
    }
    /**
     * 如果标签没有定义id，则用tag.executor作为id
     * @return
     */
    public String getResolveId() {
        return "tag.userDto";
    }
    @Override
    protected String resolveId(Element element, AbstractBeanDefinition definition, ParserContext parserContext) throws BeanDefinitionStoreException {
        String id = element.getAttribute("id");
        return StringUtils.hasText(id) ? super.resolveId(element, definition, parserContext) : getResolveId();
    }
}

UserExecutor 的 BeanDefinitionParser

public class ExecutorBeanDefineParser extends AbstractSimpleBeanDefinitionParser {
    @Override
    protected Class getBeanClass(Element element) {
        return UserExecutor.class;
    }
    @Override
    protected void doParse(Element element, ParserContext parserContext, BeanDefinitionBuilder builder) {
        BeanDefinitionRegistry registry = parserContext.getRegistry();
        String[] beanNames = registry.getBeanDefinitionNames();
        String className = "tag.executor";
        for (int i = 0; i < beanNames.length; i++) {
            String beanName = beanNames[i];
            String clazz = registry.getBeanDefinition(beanNames[i]).getBeanClassName();
            if(UserBeanDefineParser.USERDTO_CLASS.equalsIgnoreCase(clazz)){
                className = beanName;
                break;
            }
        }
        /**
         * 这里将UserDTO作为构造方法的参数，如果不需要，可以不用设置
         */
        builder.addConstructorArgReference(className);
        builder.setInitMethodName("init");
        builder.setDestroyMethodName("des");
        builder.setRole(2);
    }
    /**
     * 如果标签没有定义id，则用tag.executor作为id
     * @return
     */
    public String getResolveId() {
        return "tag.executor";
    }
    @Override
    protected String resolveId(Element element, AbstractBeanDefinition definition, ParserContext parserContext) throws BeanDefinitionStoreException {
        String id = element.getAttribute("id");
        return StringUtils.hasText(id) ? super.resolveId(element, definition, parserContext) : getResolveId();
    }
}

定义HandlerSupport

public class UserHandlerSupport extends NamespaceHandlerSupport {
    @Override
    public void init() {
        registerBeanDefinitionParser("user", new UserBeanDefineParser());
        registerBeanDefinitionParser("executor", new ExecutorBeanDefineParser());
    }
}

定义 spring.schemals和spring.handlers文件

spring.schemals文件内容

http\://www.example.org/schema/user.xsd=META-INF/user.xsd

spring.handlers文件内容

http\://www.example.org/schema/user=com.nhl.tag.handler.UserHandlerSupport

创建完成的目录结构

在resources下面创建test.xml文件进行测试。test.xml文件内容：

test测试代码如下：

public class TagTest {
    public static void main(String[] args) {
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("classpath:test.xml");
        UserDTO userDTO = applicationContext.getBean(UserDTO.class);
        // 下面打印成功，说明Bean  UserDTO 注册成功，且数据初始化成功
        System.out.println(JSONObject.toJSONString(userDTO));
        UserExecutor userExecutor = applicationContext.getBean(UserExecutor.class);
        // 下面打印成功，说明Bean  UserExecutor  注册成功，且数据初始化成功
        System.out.println(JSONObject.toJSONString(userExecutor));

        DefaultListableBeanFactory beanFactory = (DefaultListableBeanFactory) applicationContext.getAutowireCapableBeanFactory();
        String[] beanDefintionNames = beanFactory.getBeanDefinitionNames();
        String beanId = "";
        for(String beanDefintionName : beanDefintionNames){
            Class clazz = applicationContext.getBean(beanDefintionName).getClass();
            if(clazz == UserDTO.class){
                beanId = beanDefintionName;
                break;
            }

        }
        // 执行完下单打印  UserExecutor: destroy
        beanFactory.removeBeanDefinition(beanId);
    }
}

执行结果：