Mybatis sql语句改变后，自动加载（xml和注解方式）

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本文介绍了一个自定义的MyBatis映射文件热更新机制，通过监听XML映射文件和Mapper类的变化来实现自动刷新配置，适用于开发过程中频繁修改映射文件的场景。
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import java.io.File;

import java.io.IOException;

import java.lang.reflect.Field;

import java.net.URL;

import java.util.Collection;

import java.util.HashMap;

import java.util.Iterator;

import java.util.Map;

import java.util.Set;

import java.util.concurrent.Executors;

import java.util.concurrent.ScheduledExecutorService;

import java.util.concurrent.TimeUnit;

import org.apache.ibatis.binding.MapperRegistry;

import org.apache.ibatis.builder.xml.XMLMapperBuilder;

import org.apache.ibatis.executor.ErrorContext;

import org.apache.ibatis.session.Configuration;

import org.apache.ibatis.session.SqlSessionFactory;

import org.apache.log4j.Logger;

import org.mybatis.spring.SqlSessionFactoryBean;

import org.springframework.beans.BeansException;

import org.springframework.beans.factory.DisposableBean;

import org.springframework.beans.factory.InitializingBean;

import org.springframework.context.ApplicationContext;

import org.springframework.context.ApplicationContextAware;

import org.springframework.context.ConfigurableApplicationContext;

import org.springframework.core.NestedIOException;

import org.springframework.core.io.Resource;

/**

 * 

 * <p>

 * </p>

 * 

 * @author 吕兵峰 2014-2-19 上午11:56:47

 * @version V1.0

 * @modificationHistory 如有逻辑或功能性重大变更记录，请修改一下以下内容

 * @modify by user: {修改人} 2014-2-19

 * @modify by reason:{方法名}:{原因}

 */

public class MyMapperLoader implements DisposableBean, InitializingBean,

        ApplicationContextAware {

    private Logger logger = Logger.getLogger(MyMapperLoader.class);

    private ConfigurableApplicationContext context = null;

    private HashMap<String, String> fileMapping = new HashMap<String, String>();

    private Scanner scanner = null;

    private ScheduledExecutorService service = null;

    private Resource[] resources = null;

    private File[] mapperFiles;

    private Collection<Class<?>> mappers;

    @Override

    public void setApplicationContext(ApplicationContext applicationContext)

            throws BeansException {

        this.context = (ConfigurableApplicationContext) applicationContext;

    }

    @Override

    public void afterPropertiesSet() throws Exception {

        try {

            service = Executors.newScheduledThreadPool(1);

            // 获取xml

            SqlSessionFactoryBean sessionFactoryBean = context

                    .getBean(SqlSessionFactoryBean.class);

            Field field = sessionFactoryBean.getClass().getDeclaredField(

                    "mapperLocations");

            field.setAccessible(true);

            resources = (Resource[]) field.get(sessionFactoryBean);

            //获取mapper的class

            SqlSessionFactory factory = context

                    .getBean(SqlSessionFactory.class);

            Configuration configuration = factory.getConfiguration();

            mappers = configuration.getMapperRegistry().getMappers();

            mapperFiles = new File[mappers.size()];

            Iterator<Class<?>> iterator = mappers.iterator();

            int i = 0;

            while (iterator.hasNext()) {

                Class<?> class1 = (Class<?>) iterator.next();

                URL url = new URL(class1.getResource("")

                        + class1.getSimpleName() + ".class");

                mapperFiles[i++] = new File(url.getFile());

            }

            // 触发文件监听事件

            scanner = new Scanner();

            scanner.scan();

            service.scheduleAtFixedRate(new Task(), 5, 5, TimeUnit.SECONDS);

        } catch (Exception e1) {

            e1.printStackTrace();

        }

    }

    class Task implements Runnable {

        @Override

        public void run() {

            try {

                if (scanner.isChanged()) {

                    logger.debug("文件改变,重新加载.");

                    System.out.println("");

                    scanner.reload();

                    logger.debug("加载完毕.");

                }

            } catch (Exception e) {

                e.printStackTrace();

            }

        }

    }

    @SuppressWarnings({ "rawtypes" })

    class Scanner {

        public void reload() throws Exception {

            SqlSessionFactory factory = context

                    .getBean(SqlSessionFactory.class);

            Configuration configuration = factory.getConfiguration();

            // 移除加载项

            removeConfig(configuration);

            // 重新扫描加载xml

            if (resources != null) {

                for (int i = 0; i < resources.length; i++) {

                    if (resources[i] == null) {

                        continue;

                    }

                    try {

                        XMLMapperBuilder xmlMapperBuilder = new XMLMapperBuilder(

                                resources[i].getInputStream(), configuration,

                                resources[i].toString(),

                                configuration.getSqlFragments());

                        xmlMapperBuilder.parse();

                    } catch (Exception e) {

                        throw new NestedIOException(

                                "Failed to parse mapping resource: '"

                                        + resources[i] + "'", e);

                    } finally {

                        ErrorContext.instance().reset();

                    }

                }

            }

            // 重新扫描加载class

            Field f = Configuration.class.getDeclaredField("mapperRegistry");

            f.setAccessible(true);

            f.set(configuration, new MapperRegistry(configuration));

            Iterator<Class<?>> iterator = mappers.iterator();

            while (iterator.hasNext()) {

                Class<?> class1 = (Class<?>) iterator.next();

                configuration.addMapper(class1);

            }

        }

        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();

        }

        public void scan() throws IOException {

            if (!fileMapping.isEmpty()) {

                return;

            }

            if (resources != null) {

                for (int i = 0; i < resources.length; i++) {

                    String multi_key = getValue(resources[i]);

                    fileMapping.put(resources[i].getFilename(), multi_key);

                }

            }

            if (mapperFiles != null) {

                for (int i = 0; i < mapperFiles.length; i++) {

                    fileMapping.put(mapperFiles[i].getAbsolutePath(),

                            mapperFiles[i].lastModified() + "");

                }

            }

        }

        private String getValue(Resource resource) throws IOException {

            String contentLength = String.valueOf((resource.contentLength()));

            String lastModified = String.valueOf((resource.lastModified()));

            return new StringBuilder(contentLength).append(lastModified)

                    .toString();

        }

        public boolean isChanged() throws IOException {

            boolean isChanged = false;

            if (resources != null) {

                for (int i = 0; i < resources.length; i++) {

                    String name = resources[i].getFilename();

                    String value = fileMapping.get(name);

                    String multi_key = getValue(resources[i]);

                    if (!multi_key.equals(value)) {

                        isChanged = true;

                        fileMapping.put(name, multi_key);

                    }

                }

            }

            if (mapperFiles != null) {

                for (int i = 0; i < mapperFiles.length; i++) {

                    String name = mapperFiles[i].getAbsolutePath();

                    String preValue = fileMapping.get(name);

                    String curValue = mapperFiles[i].lastModified() + "";

                    if (!curValue.equals(preValue)) {

                        isChanged = true;

                        fileMapping.put(name, curValue);

                    }

                }

            }

            return isChanged;

        }

    }

    @Override

    public void destroy() throws Exception {

        if (service != null) {

            service.shutdownNow();

        }

    }

}