Mybatis中mapper.xml实现热加载介绍
作者：程序猿小白菜
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背景
有些需求可能更新sql的频率较高，但又不想频繁发布java应用程序，所以mybatis-mapper.xml热加载的需求顺势而出。
目的
只需调起加载mapper.xml的程序，无需重启整个java应用，低耦合。
实现方式
mapper.xml可以指定路径。如springboot工程resources目录下；亦可独立维护在某个git仓库，然后由程序加载到运行机器上去。
具体加载git仓库到运行机器代码如下：
package com.jason.git;
import org.apache.commons.lang3.StringUtils;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.eclipse.jgit.api.CloneCommand;
import org.eclipse.jgit.api.Git;
import org.eclipse.jgit.api.PullResult;
import org.eclipse.jgit.api.errors.GitAPIException;
import org.eclipse.jgit.transport.UsernamePasswordCredentialsProvider;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Repository;
import java.io.File;
import java.io.IOException;
/**
* @author jason
* @create 2022/1/19 11:39 上午
**/
@Repository
public class GitConfigRepository {
private static final long MIN_CHECKOUT_INTERVAL = 1000L * 10;
private static final long MAX_LOCAL_LIFE_CYCLE = 2 * 86400 * 1000L;
private Log log = LogFactory.getLog(GitConfigRepository.class);
@Value("${git.repository:}")
private String gitRepositoryURL;
@Value("${git.branch:master}")
private String gitBranch;
@Value("${git.username:}")
private String gitUsername;
@Value("${git.password:}")
private String gitPassword;
@Value("${bi.meta.git.localRepository:}")
private String localRepository;
private long lastCheckoutTimestamp;
private long localRepositoryTimestamp;
private File gitDir;
private Git git;
public File getRepositoryDir() throws IOException, GitAPIException {
long now = System.currentTimeMillis();
if (now - lastCheckoutTimestamp > MIN_CHECKOUT_INTERVAL) {
this.lastCheckoutTimestamp = now;
if (StringUtils.isNotEmpty(localRepository)) {
gitDir = new File(localRepository);
} else {
boolean isNewDir = false;
if (gitDir != null && !gitDir.exists()) {
gitDir = null;
}
if (gitDir != null) {
if (now - localRepositoryTimestamp > MAX_LOCAL_LIFE_CYCLE) {
localRepositoryTimestamp = 0;
try {
gitDir.delete();
} catch (Exception e) {
// do nothing
}
gitDir = null;
}
File keyFile = new File(gitDir, "global/config/config.yml");
if (!(keyFile.exists() && keyFile.length() > 0)) {
try {
gitDir.delete();
} catch (Exception e) {
// do nothing
}
gitDir = null;
}
}
if (gitDir == null) {
gitDir = File.createTempFile("egret-meta", ".git");
if (!gitDir.delete()) {
throw new IOException("无法删除临时文件: " + gitDir.getAbsolutePath());
}
if (!gitDir.mkdir()) {
throw new IOException("创建历史Git本地目录失败: " + gitDir.getAbsolutePath());
}
gitDir.deleteOnExit();
isNewDir = true;
localRepositoryTimestamp = now;
}
if (StringUtils.isNotEmpty(gitRepositoryURL)) {
//设置远程服务器上的用户名和密码
UsernamePasswordCredentialsProvider usernamePasswordCredentialsProvider = new
UsernamePasswordCredentialsProvider(gitUsername, gitPassword);
if (isNewDir) {
//克隆代码库命令
CloneCommand cloneCommand = Git.cloneRepository();
git = cloneCommand.setURI(gitRepositoryURL)
.setBranch(gitBranch)
.setDirectory(gitDir)
.setCredentialsProvider(usernamePasswordCredentialsProvider)
.call();
}
log.info("Checkout meta configs from. [" + gitRepositoryURL + "|" + gitBranch + "]");
PullResult call = git.pull().setRemoteBranchName(gitBranch).setCredentialsProvider(usernamePasswordCredentialsProvider).call();
log.info("Checkout meta configs OK.");
}
}
}
return gitDir;
}
}
1、手动触发
public void reloadSqlXml() {
try {
File mapperXmlDir = gitConfigRepository.getRepositoryDir();
mapperHotDeployPlugin.reloadSqlXml(mapperXmlDir);
} catch (Exception e) {
log.error(e.getMessage(), e);
}
}
package com.jason.dao;
import cn.hutool.core.bean.BeanUtil;
import lombok.extern.slf4j.Slf4j;
import org.apache.ibatis.builder.xml.XMLMapperBuilder;
import org.apache.ibatis.builder.xml.XMLMapperEntityResolver;
import org.apache.ibatis.executor.ErrorContext;
import org.apache.ibatis.parsing.XPathParser;
import org.apache.ibatis.session.Configuration;
import org.apache.ibatis.session.SqlSessionFactory;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import java.io.File;
import java.io.FileInputStream;
import java.util.*;
import java.util.stream.Collectors;
/**
* mapper.xml热部署，最小单位是一个xml文件
*
* @author: jason
* @Date: 2022-01-13
*/
@Slf4j
@Component
public class MapperHotDeployPlugin implements InitializingBean {
@Autowired
private SqlSessionFactory sqlSessionFactory;
private volatile Configuration configuration;
@Override
public void afterPropertiesSet() {
configuration = sqlSessionFactory.getConfiguration();
}
public void reloadSqlXml(File file) {
if (file == null) {
return;
}
List<File> fileList = new ArrayList<>();
setFiles(file, fileList, ".xml");
reloadXml(fileList);
}
private void setFiles(File file, List<File> fileList, String suffix) {
File[] files = file.listFiles();
if (files == null || files.length == 0) {
return;
}
for (File f : files) {
if (f.isDirectory()) {
//递归调用
setFiles(f, fileList, suffix);
} else {
//保存文件路径到集合中
if (f.getAbsolutePath().contains(suffix)) {
fileList.add(f);
}
}
}
}
/**
* 重新加载sql.xml
*
* @param fileList 修改的xml资源
*/
private void reloadXml(List<File> fileList) {
log.info("需要重新加载的文件列表: {}", fileList);
fileList.forEach(r -> {
try {
clearMap(getNamespace(r));
clearSet(r.getAbsolutePath());
XMLMapperBuilder xmlMapperBuilder =
new XMLMapperBuilder(new FileInputStream(r), getTarConfiguration(), r.toString(),
getTarConfiguration().getSqlFragments());
xmlMapperBuilder.parse();
} catch (Exception e) {
log.info("ERROR: 重新加载[{}]失败", r.toString(), e);
throw new RuntimeException("ERROR: 重新加载[" + r.toString() + "]失败", e);
} finally {
ErrorContext.instance().reset();
}
});
log.info("成功热部署文件列表: {}", fileList);
}
private Configuration getTarConfiguration() {
return configuration;
}
/**
* 删除xml元素的节点缓存
*
* @param nameSpace xml中命名空间
*/
private void clearMap(String nameSpace) {
log.info(
"清理Mybatis的namespace={}在mappedStatements、caches、resultMaps、parameterMaps、keyGenerators、sqlFragments中的缓存");
Arrays.asList("mappedStatements", "caches", "resultMaps", "parameterMaps", "keyGenerators", "sqlFragments")
.forEach(fieldName -> {
Object value = BeanUtil.getFieldValue(getTarConfiguration(), fieldName);
if (value instanceof Map) {
Map<?, ?> map = (Map) value;
List<Object> list = map.keySet().stream().filter(o -> o.toString().startsWith(nameSpace + "."))
.collect(Collectors.toList());
log.info("需要清理的元素: {}", list);
list.forEach(k -> map.remove((Object) k));
}
});
}
/**
* 清除文件记录缓存
*
* @param resource xml文件路径
*/
private void clearSet(String resource) {
log.info("清理mybatis的资源{}在容器中的缓存", resource);
Object value = BeanUtil.getFieldValue(getTarConfiguration(), "loadedResources");
if (value instanceof Set) {
Set<?> set = (Set) value;
set.remove(resource);
set.remove("namespace:" + resource);
}
}
/**
* 获取xml的namespace
*
* @param file xml资源
* @return java.lang.String
*/
private String getNamespace(File file) {
try {
XPathParser parser = new XPathParser(new FileInputStream(file), true, null, new XMLMapperEntityResolver());
return parser.evalNode("/mapper").getStringAttribute("namespace");
} catch (Exception e) {
log.info("ERROR: 解析xml中namespace失败", e);
throw new RuntimeException("ERROR: 解析xml中namespace失败", e);
}
}
}
2、自动监控
package com.jason.replacer.config;
import lombok.SneakyThrows;
import lombok.extern.slf4j.Slf4j;
import org.apache.ibatis.builder.xml.XMLMapperBuilder;
import org.apache.ibatis.builder.xml.XMLMapperEntityResolver;
import org.apache.ibatis.executor.ErrorContext;
import org.apache.ibatis.parsing.XPathParser;
import org.apache.ibatis.session.Configuration;
import org.apache.ibatis.session.SqlSessionFactory;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.core.io.Resource;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.stereotype.Component;
import java.lang.reflect.Field;
import java.nio.file.*;
import java.util.*;
import java.util.stream.Collectors;
/**
* mapper.xml热部署，最小单位是一个xml文件
*
* @author: jason
* @Date: 2022-01-13
*/
@Slf4j
@Component
public class MapperHotDeployPlugin implements InitializingBean {
@Autowired
private SqlSessionFactory sqlSessionFactory;
private volatile Configuration configuration;
@Value("${mybatis.mapper-locations}")
private String mybatisPath;
@Override
public void afterPropertiesSet() {
configuration = sqlSessionFactory.getConfiguration();
new WatchThread().start();
}
class WatchThread extends Thread {
@Override
public void run() {
startWatch();
}
/**
* 启动监听
*/
private void startWatch() {
try {
WatchService watcher = FileSystems.getDefault().newWatchService();
getWatchPaths().forEach(p -> {
try {
Paths.get(p).register(watcher, StandardWatchEventKinds.ENTRY_CREATE,
StandardWatchEventKinds.ENTRY_DELETE, StandardWatchEventKinds.ENTRY_MODIFY);
} catch (Exception e) {
log.error("ERROR: 注册xml监听事件", e);
throw new RuntimeException("ERROR: 注册xml监听事件", e);
}
});
while (true) {
WatchKey watchKey = watcher.take();
Set<String> set = new HashSet<>();
for (WatchEvent<?> event : watchKey.pollEvents()) {
set.add(event.context().toString());
}
// 重新加载xml
reloadXml(set);
boolean valid = watchKey.reset();
if (!valid) {
break;
}
}
} catch (Exception e) {
System.out.println("Mybatis的xml监控失败!");
log.info("Mybatis的xml监控失败!", e);
}
}
/**
* 加载需要监控的文件父路径
*
* @return java.util.Set<java.lang.String>
*/
private Set<String> getWatchPaths() {
Set<String> set = new HashSet<>();
Arrays.stream(getResource()).forEach(r -> {
try {
log.info("资源路径:{}", r.toString());
set.add(r.getFile().getParentFile().getAbsolutePath());
} catch (Exception e) {
log.info("获取资源路径失败", e);
throw new RuntimeException("获取资源路径失败");
}
});
log.info("需要监听的xml资源: {}", set);
return set;
}
/**
* 获取配置的mapperLocations
*
* @return org.springframework.core.io.Resource[]
*/
@SneakyThrows
private Resource[] getResource() {
return new PathMatchingResourcePatternResolver().getResources(mybatisPath);
}
/**
* 删除xml元素的节点缓存
*
* @param nameSpace xml中命名空间
*/
private void clearMap(String nameSpace) {
log.info(
"清理Mybatis的namespace={}在mappedStatements、caches、resultMaps、parameterMaps、keyGenerators、sqlFragments中的缓存");
Arrays.asList("mappedStatements", "caches", "resultMaps", "parameterMaps", "keyGenerators", "sqlFragments")
.forEach(fieldName -> {
Object value = getFieldValue(configuration, fieldName);
if (value instanceof Map) {
Map<?, ?> map = (Map) value;
List<Object> list =
map.keySet().stream().filter(o -> o.toString().startsWith(nameSpace + "."))
.collect(Collectors.toList());
log.info("需要清理的元素: {}", list);
list.forEach(k -> map.remove((Object) k));
}
});
}
/**
* 清除文件记录缓存
*
* @param resource xml文件路径
*/
private void clearSet(String resource) {
log.info("清理mybatis的资源{}在容器中的缓存", resource);
Object value = getFieldValue(configuration, "loadedResources");
if (value instanceof Set) {
Set<?> set = (Set) value;
set.remove(resource);
set.remove("namespace:" + resource);
}
}
/**
* 获取对象指定属性
*
* @param obj 对象信息
* @param fieldName 属性名称
* @return java.lang.Object
*/
private Object getFieldValue(Object obj, String fieldName) {
log.info("从{}中加载{}属性", obj, fieldName);
try {
Field field = obj.getClass().getDeclaredField(fieldName);
boolean accessible = field.isAccessible();
field.setAccessible(true);
Object value = field.get(obj);
field.setAccessible(accessible);
return value;
} catch (Exception e) {
log.info("ERROR: 加载对象中[{}]", fieldName, e);
throw new RuntimeException("ERROR: 加载对象中[" + fieldName + "]", e);
}
}
/**
* 重新加载set中xml
*
* @param set 修改的xml资源
*/
private void reloadXml(Set<String> set) {
log.info("需要重新加载的文件列表: {}", set);
List<Resource> list = Arrays.stream(getResource()).filter(p -> set.contains(p.getFilename()))
.collect(Collectors.toList());
log.info("需要处理的资源路径:{}", list);
list.forEach(r -> {
try {
clearMap(getNamespace(r));
clearSet(r.toString());
XMLMapperBuilder xmlMapperBuilder =
new XMLMapperBuilder(r.getInputStream(), configuration, r.toString(),
configuration.getSqlFragments());
xmlMapperBuilder.parse();
} catch (Exception e) {
log.info("ERROR: 重新加载[{}]失败", r.toString(), e);
throw new RuntimeException("ERROR: 重新加载[" + r.toString() + "]失败", e);
} finally {
ErrorContext.instance().reset();
}
});
log.info("成功热部署文件列表: {}", set);
}
/**
* 获取xml的namespace
*
* @param resource xml资源
* @return java.lang.String
*/
private String getNamespace(Resource resource) {
log.info("从{}获取namespace", resource.toString());
try {
XPathParser parser =
new XPathParser(resource.getInputStream(), true, null, new XMLMapperEntityResolver());
return parser.evalNode("/mapper").getStringAttribute("namespace");
} catch (Exception e) {
log.info("ERROR: 解析xml中namespace失败", e);
throw new RuntimeException("ERROR: 解析xml中namespace失败", e);
}
}
}
}
注
上面提供了加载mapper.xml文件的两种方式
读取文件绝对路径
public static List<File> getFiles(String dirPath) {
List<File> fileList = new ArrayList<>();
File file = new File(dirPath);
return getFiles(file, fileList, ".xml");
}
public static List<File> getFiles(File file, List<File> fileList, String suffix) {
File[] files = file.listFiles();
if (files == null || files.length == 0) {
return Collections.emptyList();
}
for (File f : files) {
if (f.isDirectory()) {
//递归调用
getFiles(f, fileList, suffix);
} else {
//保存文件路径到集合中
if (f.getAbsolutePath().contains(suffix)) {
fileList.add(f);
}
}
}
return fileList;
}
读取classpath下的资源路径
@SneakyThrows
private Resource[] getResource() {
return new PathMatchingResourcePatternResolver().getResources("classpath:mappers/**/*.xml");
}
总结
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