Mybatis Mapper配置XML文件热加载实现

日常开发中数据持久层, 我大多选用mybatis, 轻量化和可控性高, sql掌握在自己手里, 感觉踏实一些.
但是从ibatis到mybatis以来, 一直有个十分困扰我的问题, 就是mapperXML文件的热加载问题, 相信这也同样困扰着不少同行们.

这几天实在忍无可忍, 于是在网上搜索了一番, 找了找思路, 结合网上的几个例子改了一个工具类出来, 可解决热加载问题.
实际测试有效, 终于可以摆脱改下SQL必须重启的命运了.

import org.apache.ibatis.builder.xml.XMLMapperBuilder;
import org.apache.ibatis.session.Configuration;
import org.apache.ibatis.session.SqlSessionFactory;
import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.core.io.Resource;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;

import java.io.IOException;
import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

public class XMLMapperReloader implements ApplicationContextAware {

    private ConfigurableApplicationContext context = null;
    private HashMap<String, Long> fileMapping = new HashMap<String, Long>();
    private Scanner scanner = null;
    private String packageSearchPath;
    private ScheduledExecutorService service = null;

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.context = (ConfigurableApplicationContext) applicationContext;

    }

    public XMLMapperReloader(){
        service = Executors.newScheduledThreadPool(1);
        service.scheduleAtFixedRate(new Task(), 5, 5, TimeUnit.SECONDS);
    }

    class Task implements Runnable {
        @Override
        public void run() {
            try {
                scanner = new Scanner();
                scanner.refreshMapper();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }

    }

    @SuppressWarnings({ "rawtypes" })
    class Scanner {
        private Resource[] mapperLocations;

        public void refreshMapper() {
            try {
                SqlSessionFactory factory = context.getBean(SqlSessionFactory.class);
                Configuration configuration = factory.getConfiguration();

                // step.1 扫描文件
                try {
                    this.scanMapperXml();
                } catch (IOException e) {
                    return;
                }

                // step.2 判断是否有文件发生了变化
                if (this.isChanged()) {
                    System.out.println("==============检测到mapper有改变, 开始刷新...===============");
                    // step.2.1 清理
                    this.removeConfig(configuration);

                    // step.2.2 重新加载
                    for (Resource configLocation : mapperLocations) {
                        try {
                            XMLMapperBuilder xmlMapperBuilder = new XMLMapperBuilder(configLocation.getInputStream(), configuration, configLocation.toString(), configuration.getSqlFragments());
                            xmlMapperBuilder.parse();
                        } catch (IOException e) {
                            continue;
                        }
                    }
                    System.out.println("==============mapper刷新完毕===============");
                }


            } catch (Exception e) {
                e.printStackTrace();
            }
        }

        private void scanMapperXml() throws IOException {
            this.mapperLocations = new PathMatchingResourcePatternResolver().getResources(packageSearchPath);
        }

        private void removeConfig(Configuration configuration) throws Exception {
            Class<?> classConfig = configuration.getClass();
            clearMap(classConfig, configuration, "mappedStatements");
            clearMap(classConfig, configuration, "caches");
            clearMap(classConfig, configuration, "resultMaps");
            clearMap(classConfig, configuration, "parameterMaps");
            clearMap(classConfig, configuration, "keyGenerators");
            clearMap(classConfig, configuration, "sqlFragments");

            clearSet(classConfig, configuration, "loadedResources");

        }

        private void clearMap(Class<?> classConfig, Configuration configuration, String fieldName) throws Exception {
            Field field = classConfig.getDeclaredField(fieldName);
            field.setAccessible(true);
            Map mapConfig = (Map) field.get(configuration);
            mapConfig.clear();
        }

        private void clearSet(Class<?> classConfig, Configuration configuration, String fieldName) throws Exception {
            Field field = classConfig.getDeclaredField(fieldName);
            field.setAccessible(true);
            Set setConfig = (Set) field.get(configuration);
            setConfig.clear();
        }

        private boolean isChanged() throws IOException {
            boolean flag = false;
            for (Resource resource : mapperLocations) {
                String resourceName = resource.getFilename();

                boolean addFlag = !fileMapping.containsKey(resourceName);// 此为新增标识

                // 修改文件:判断文件内容是否有变化
                Long compareFrame = fileMapping.get(resourceName);
                long lastFrame = resource.contentLength() + resource.lastModified();
                boolean modifyFlag = null != compareFrame && compareFrame.longValue() != lastFrame;// 此为修改标识

                // 新增或是修改时,存储文件
                if(addFlag || modifyFlag) {
                    fileMapping.put(resourceName, Long.valueOf(lastFrame));// 文件内容帧值
                    flag = true;
                }
            }
            return flag;
        }
    }

    public String getPackageSearchPath() {
        return packageSearchPath;
    }

    public void setPackageSearchPath(String packageSearchPath) {
        this.packageSearchPath = packageSearchPath;
    }
}

这个工具类加入项目后, 还需要配置一个bean.

<bean id="XMLMapperReloader" class="com.xx.xx.dao.XMLMapperReloader">
    <property name="packageSearchPath" value="classpath:com/xx/xx/dao/*/*.xml"/>
</bean>

注意 packageSearchPath 这个属性的值和mybatis的sqlSessionFactory的mapperLocations配置一样.

<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
    <property name="dataSource" ref="dataSource" />
    <property name="configLocation" value="classpath:mybatis-config.xml"/>
    <property name="mapperLocations" value="classpath:com/xx/xx/dao/*/*.xml" />
</bean>