Mybatis中mapper.xml实现热加载介绍

目录

• 背景
• 目的
• 实现方式
• 总结

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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