mybatis应用程序，由于是半自动化的sql, 有大量的sql是在xml文件中配置的，而在开发程序的过程中，通常需要边写sql变调试应用。但在默认情况下，xml文件里配置的sql语句是被放入到缓存中去了，每次更改有sql语句的xml文件，需要重新启动应用，这样工作效率很低，于是很希望有一个动态加载xml文件的功能，自动加载新的sql语句，并重新写入到缓存中，在网上参考了很多资料，最终弄了一个简单的东西出来，直接写成了spring mvc的controller。代码如下: 
 

package com.yihaomen.controller;
import java.io.IOException;
import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.ibatis.builder.xml.XMLMapperBuilder;
import org.apache.ibatis.session.Configuration;
import org.apache.ibatis.session.SqlSessionFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Scope;
import org.springframework.core.io.Resource;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
@Scope("prototype")
@Controller
@RequestMapping("/sql")
public class SQLSessionCacheController {private Log log  = LogFactory.getLog(SQLSessionCacheController.class);@Autowiredprivate SqlSessionFactory sqlSessionFactory;private Resource[] mapperLocations;private String packageSearchPath = "classpath*:**/mappers/*.xml";private HashMap<String, Long> fileMapping = new HashMap<String, Long>();// 记录文件是否变化@RequestMapping("/refresh")@ResponseBodypublic String refreshMapper() {try {Configuration configuration = this.sqlSessionFactory.getConfiguration();// step.1 扫描文件try {this.scanMapperXml();} catch (IOException e) {log.error("packageSearchPath扫描包路径配置错误");return "packageSearchPath扫描包路径配置错误";}System.out.println("==============刷新前mapper中的内容===============");for (String name : configuration.getMappedStatementNames()) {System.out.println(name);}// step.2 判断是否有文件发生了变化if (this.isChanged()) {// 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();log.info("mapper文件[" + configLocation.getFilename() + "]缓存加载成功");} catch (IOException e) {log.error("mapper文件[" + configLocation.getFilename() + "]不存在或内容格式不对");continue;}}}System.out.println("==============刷新后mapper中的内容===============");for (String name : configuration.getMappedStatementNames()) {System.out.println(name);}return "刷新mybatis xml配置语句成功";} catch (Exception e) {e.printStackTrace();return "刷新mybatis xml配置语句失败";}}public void setPackageSearchPath(String packageSearchPath) {this.packageSearchPath = packageSearchPath;}public void setSqlSessionFactory(SqlSessionFactory sqlSessionFactory) {this.sqlSessionFactory = sqlSessionFactory;}/*** 扫描xml文件所在的路径* @throws IOException */private void scanMapperXml() throws IOException {this.mapperLocations = new PathMatchingResourcePatternResolver().getResources(packageSearchPath);}/*** 清空Configuration中几个重要的缓存* @param configuration* @throws Exception*/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");}@SuppressWarnings("rawtypes")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();}@SuppressWarnings("rawtypes")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();}/*** 判断文件是否发生了变化* @param resource* @return* @throws IOException*/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;}
}

注意事项： 
在我的应用中，mybatis配置文件放在这里的：classpath*:**/mappers/*.xml， 因此我定义死了，需要修改成自己的路径. 

测试方法： 
可以通过controller提供的地址，直接在浏览器上输入url访问, 比如: http://localhost:8080/sql/refresh , 当然，你还可以通过js用ajax方式调用，都是可以的。