Mybatis热加载Mapper.xml

开发的时候，写Mybatis Mapper.xml文件的时候，每次修改SQL都需要重启服务，感觉十分麻烦，于是尝试写了一个Mybatis的Mapper.xml热加载。

能在修改Mapper.xml之后重新加载Mybatis，开发的时候可以用一下。

Spring配置：

<bean id="MybatisMapperDynamicLoader" class="com.teststartup.MybatisMapperDynamicLoader" />

Java代码：

import java.io.IOException;
import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.Timer;
import java.util.TimerTask;
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.springframework.beans.BeansException;
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;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.core.io.support.ResourcePatternResolver;

public class MybatisMapperDynamicLoader implements InitializingBean, ApplicationContextAware {
private final HashMap<String, String> mappers = new HashMap<String, String>();
private volatile ConfigurableApplicationContext context = null;
private volatile Scanner scanner = null;

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

@Override
public void afterPropertiesSet() throws Exception {
try {
scanner = new Scanner();
new Timer(true).schedule(new TimerTask() {
public void run() {
try {
if (scanner.isChanged()) {
System.out.println("load mapper.xml");
scanner.reloadXML();
}
} catch (Exception e) {
e.printStackTrace();
}
}
}, 10 * 1000, 5 * 1000);
} catch (Exception e1) {
e1.printStackTrace();
}
}

@SuppressWarnings("unchecked")
class Scanner {
private static final String XML_RESOURCE_PATTERN = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX + "**/*Sql.xml";
private final ResourcePatternResolver resourcePatternResolver = new PathMatchingResourcePatternResolver();

public Scanner() throws IOException {
Resource[] resources = findResource();
if (resources != null) {
for (Resource resource : resources) {
String key = resource.getURI().toString();
String value = getMd(resource);
mappers.put(key, value);
}
}
}

public void reloadXML() throws Exception {
SqlSessionFactory factory = context.getBean(SqlSessionFactory.class);
Configuration configuration = factory.getConfiguration();
removeConfig(configuration);
for (Resource resource : findResource()) {
try {
XMLMapperBuilder xmlMapperBuilder = new XMLMapperBuilder(resource.getInputStream(), configuration, resource.toString(),
configuration.getSqlFragments());
xmlMapperBuilder.parse();
} finally {
ErrorContext.instance().reset();
}
}
}

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) field.get(configuration)).clear();
}

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

public boolean isChanged() throws IOException {
boolean isChanged = false;
for (Resource resource : findResource()) {
String key = resource.getURI().toString();
String value = getMd(resource);
if (!value.equals(mappers.get(key))) {
isChanged = true;
mappers.put(key, value);
}
}
return isChanged;
}

private Resource[] findResource() throws IOException {
return resourcePatternResolver.getResources(XML_RESOURCE_PATTERN);
}

private String getMd(Resource resource) throws IOException {
return new StringBuilder().append(resource.contentLength()).append("-").append(resource.lastModified()).toString();
}
}
}