关于Spring+MyBatis的MapperScannerConfigurer无法加载place-holder属性问题分析

在1.2.5以下版本的mybatis-spring一下配置可能会无法启动，但junit方式可以启动

配置：

<bean id="sqlSessionFactoryName" class="org.mybatis.spring.SqlSessionFactoryBean">
<property name="dataSource" ref="dataSource" />
<property name="configLocation"
      value="${dao.mybatis.sqlSessionFactory.configLocation}" />
</bean>
经分析1.2.5以下的mybatis-spring的MapperScannerConfigurer中判断是否为GenericApplicationContext的实例
启动时不为GenericApplicationContext的实例时属性无法加载
1.3.1以后版本已经修改
<bean id="mapperScannerConfigurer" class="org.mybatis.spring.mapper.MapperScannerConfigurer">
    <!--以下两个参数解决连接池属性无法加载问题-->
   <property name="sqlSessionFactoryBeanName" value="sqlSessionFactoryName"/>
   <property name="processPropertyPlaceHolders" value="true"/>
   <property name="basePackage" value="${dao.mybatis.scanner.basePackage}" /> 
</bean>

到此Mybatis本身的属性已经可以正常加载了，但在正式环境中可能会碰到xml中其他注入属性无法加载，如Dubbo的配置信息注入
经分析原因在于MapperScannerConfigurer中的代码有问题。
private void processPropertyPlaceHolders() {
    Map prcs = this.applicationContext.getBeansOfType(PropertyResourceConfigurer.class);
    if(!prcs.isEmpty() && this.applicationContext instanceof ConfigurableApplicationContext) {
    红色这一行代码会导致在属性加载前加载dubbo的xml文件中定义的bean，导致属性未注入
解决方法如下：
    新建对象继承MapperScannerConfigurer，注入自定义属性在开始扫描前加载，示例如下：
    
    

import org.mybatis.spring.mapper.MapperScannerConfigurer;
import org.springframework.beans.MutablePropertyValues;
import org.springframework.beans.PropertyValue;
import org.springframework.beans.PropertyValues;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.config.PropertyResourceConfigurer;
import org.springframework.beans.factory.config.TypedStringValue;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.support.DefaultListableBeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ConfigurableApplicationContext;

import java.util.Iterator;
import java.util.Map;
import java.util.Properties;

/**
 *  
 */
public class SelfMapperScannerConfigurer extends MapperScannerConfigurer {
    private ApplicationContext applicationContext;
    private String beanName;
    private String preLoadPropBeanName;

    public void setApplicationContext(ApplicationContext applicationContext) {
        super.setApplicationContext(applicationContext);
        this.applicationContext = applicationContext;
    }

    @Override
    public void setBeanName(String name) {
        this.beanName = name;
        super.setBeanName(name);
    }

    public void setPreLoadPropBeanName(String preLoadPropBeanName) {
        this.preLoadPropBeanName = preLoadPropBeanName;
    }

    public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
        if (this.preLoadPropBeanName != null) {
            preloadPropertyResource();
            this.setProcessPropertyPlaceHolders(false);
        }
        super.postProcessBeanDefinitionRegistry(registry);

    }

    private void preloadPropertyResource() {
        if (applicationContext.containsBean(this.preLoadPropBeanName)) {
            BeanDefinition mapperScannerBean = ((ConfigurableApplicationContext) this.applicationContext).getBeanFactory().getBeanDefinition(this.beanName);
            DefaultListableBeanFactory factory = new DefaultListableBeanFactory();
            factory.registerBeanDefinition(this.beanName, mapperScannerBean);
            PropertyResourceConfigurer configurer = applicationContext.getBean(this.preLoadPropBeanName, PropertyResourceConfigurer.class);
            configurer.postProcessBeanFactory(factory);
            if (applicationContext.containsBean("propertyConfigurer")) {
                configurer = applicationContext.getBean(this.preLoadPropBeanName, PropertyResourceConfigurer.class);
                configurer.postProcessBeanFactory(factory);
            }

            MutablePropertyValues values1 = mapperScannerBean.getPropertyValues();
            String basePackage = this.updatePropertyValue("basePackage", values1);
            String sqlSessionFactoryBeanName = this.updatePropertyValue("sqlSessionFactoryBeanName", values1);
            String sqlSessionTemplateBeanName = this.updatePropertyValue("sqlSessionTemplateBeanName", values1);
            this.setBasePackage(basePackage);
            this.setSqlSessionFactoryBeanName(sqlSessionFactoryBeanName);
            this.setSqlSessionTemplateBeanName(sqlSessionTemplateBeanName);


        }
    }


    private String updatePropertyValue(String propertyName, PropertyValues values) {
        PropertyValue property = values.getPropertyValue(propertyName);
        String rst = null;
        if (property == null) {
            return null;
        } else {
            Object value = property.getValue();
            rst = value == null ? null : (value instanceof String ? value.toString() : (value instanceof TypedStringValue ? ((TypedStringValue) value).getValue() : null));
        }
        return rst;
    }
}
修改配置：
<bean id="mapperScannerConfigurer" class="XX.SelfMapperScannerConfigurer">
   <property name="sqlSessionFactoryBeanName" value="sqlSessionFactoryName"/>
   <property name="processPropertyPlaceHolders" value="true"/>
   <property name="basePackage" value="${dao.mybatis.scanner.basePackage}" />
   <!--mybatis需要的属性文件注入，会忽略掉processPropertyPlaceHolders配置-->
   <property name="preLoadPropBeanName" value="propertyPlaceholderConfigurer"/>
</bean>