业务场景
业务场景：首先项目进行分布式拆分之后，按照模块再分为为api层和service层，web层。
其中订单业务的实体类放在com.muses.taoshop.item.entity，而用户相关的实体类放在com.muses.taoshop.user.entity。所以就这样，通过通配符方式去setTypeAliasesPackage ，com.muses.taoshop.*.entity
Ant通配符的3中风格：
(1) ?：匹配文件名中的一个字符 eg: com/test/entity? 匹配 com/test/entityaa
(2) * : 匹配文件名中的任意字符 eg: com/*/entity 匹配 com/test/entity
(3) ** ： 匹配文件名中的多重路径 eg: com/**/entity 匹配 com/test/test1/entity
mybatis配置类写在common工程，数据库操作有些是可以共用的，不需要每个web工程都进行重复配置。
所以写了个Mybatis配置类：
package com.muses.taoshop.common.core.database.config;
public class BaseConfig {
/**
* 设置主数据源名称
*/
public static final String DATA_SOURCE_NAME = "shop";
/**
* 加载配置文件信息
*/
public static final String DATA_SOURCE_PROPERTIES = "spring.datasource.shop";
/**
* repository 所在包
*/
public static final String REPOSITORY_PACKAGES = "com.muses.taoshop.**.repository";
/**
* mapper 所在包
*/
public static final String MAPPER_PACKAGES = "com.muses.taoshop.**.mapper";
/**
* 实体类 所在包
*/
public static final String ENTITY_PACKAGES = "com.muses.taoshop.*.entity";
...
}
贴一下配置类代码，主要关注： factoryBean.setTypeAliasesPackage(ENTITY_PACKAGES);之前的写法是这样的。ENTITY_PACKAGES是个常量：public static final String ENTITY_PACKAGES = "com.muses.taoshop.*.entity";，ps：注意了，这里用了通配符
package com.muses.taoshop.common.core.database.config;
//省略代码
@MapperScan(
basePackages = MAPPER_PACKAGES,
annotationClass = MybatisRepository.class,
sqlSessionFactoryRef = SQL_SESSION_FACTORY
)
@EnableTransactionManagement
@Configuration
public class MybatisConfig {
//省略其它代码，主要看sqlSessionFactory配置
@Primary
@Bean(name = SQL_SESSION_FACTORY)
public SqlSessionFactory sqlSessionFactory(@Qualifier(DATA_SOURCE_NAME)DataSource dataSource)throws Exception{
//SpringBoot默认使用DefaultVFS进行扫描，但是没有扫描到jar里的实体类
VFS.addImplClass(SpringBootVFS.class);
SqlSessionFactoryBean factoryBean = new SqlSessionFactoryBean();
factoryBean.setDataSource(dataSource);
//factoryBean.setConfigLocation(new ClassPathResource("mybatis-config.xml"));
ResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
try{
factoryBean.setMapperLocations(resolver.getResources("classpath*:/mybatis/*Mapper.xml"));
//String typeAliasesPackage = packageScanner.getTypeAliasesPackages();
//设置一下TypeAliasesPackage
factoryBean.setTypeAliasesPackage(ENTITY_PACKAGES);
SqlSessionFactory sqlSessionFactory = factoryBean.getObject();
return sqlSessionFactory;
}catch (Exception e){
e.printStackTrace();
throw new RuntimeException();
}
}
...
}
ps:原先做法：在sqlSessionFactory方法里进行TypeAliasesPackage设置，(让Mybatis能够扫描到实体类，在xml文件里就不需要写全实体类的全包名了。)factoryBean.setTypeAliasesPackage(ENTITY_PACKAGES);
但是运行之后都会报错，提示实体类不能扫描到，因为我的service工程里都是这样写的，ResultType进行用别名ItemCategory，例子：
<!-- 获取所有的商品品类信息-->
<select id="listCategory" resultType="ItemCategory">
SELECT
<include refid="BaseColumnList" />
FROM item_category t
</select>
源码简单分析
针对上面的业务场景，首先的分析一下，我们知道Mybatis的执行都会通过SQLSessionFactory去调用，调用前都是先用SqlSessionFactoryBean的setTypeAliasesPackage可以看一下SqlSessionFactoryBean的源码：
/**
* Packages to search for type aliases.
*
* @since 1.0.1
*
* @param typeAliasesPackage package to scan for domain objects
*
*/
public void setTypeAliasesPackage(String typeAliasesPackage) {
this
我们看一下SqlSessionFactoryBean的初步Build方法：
/**
* Build a {@code SqlSessionFactory} instance.
*
* The default implementation uses the standard MyBatis {@code XMLConfigBuilder} API to build a
* {@code SqlSessionFactory} instance based on an Reader.
* Since 1.3.0, it can be specified a {@link Configuration} instance directly(without config file).
*
* @return SqlSessionFactory
* @throws IOException if loading the config file failed
*/
protected SqlSessionFactory buildSqlSessionFactory() throws IOException {
Configuration configuration;
//创建一个XMLConfigBuilder读取配置文件的一些信息
XMLConfigBuilder xmlConfigBuilder = null;
if (this.configuration != null) {
configuration = this.configuration;
if (configuration.getVariables() == null) {
configuration.setVariables(this.configurationProperties);
} else if (this.configurationProperties != null) {
configuration.getVariables().putAll(this.configurationProperties);//添加Properties属性
}
} else if (this.configLocation != null) {
xmlConfigBuilder = new XMLConfigBuilder(this.configLocation.getInputStream(), null, this.configurationProperties);
configuration = xmlConfigBuilder.getConfiguration();
} else {
if (LOGGER.isDebugEnabled()) {
LOGGER.debug("Property 'configuration' or 'configLocation' not specified, using default MyBatis Configuration");
}
configuration = new Configuration();
if (this.configurationProperties != null) {
configuration.setVariables(this.configurationProperties);
}
}
if (this.objectFactory != null) {
configuration.setObjectFactory(this.objectFactory);
}
if (this.objectWrapperFactory != null) {
configuration.setObjectWrapperFactory(this.objectWrapperFactory);
}
if (this.vfs != null) {
configuration.setVfsImpl(this.vfs);
}
/*
重点看这里，其它源码先不看，这里获取到typeAliasesPackage字符串之后，调用tokenizeToStringArray进行字符串分隔返回一个数组，`String CONFIG_LOCATION_DELIMITERS = ",; \t\n";`
*/
if (hasLength(this.typeAliasesPackage)) {
String[] typeAliasPackageArray = tokenizeToStringArray(this.typeAliasesPackage,
ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS);
for (String packageToScan : typeAliasPackageArray) {//遍历，注册到configuration对象上
configuration.getTypeAliasRegistry().registerAliases(packageToScan,
typeAliasesSuperType == null ? Object.class : typeAliasesSuperType);
if (LOGGER.isDebugEnabled()) {
LOGGER.debug("Scanned package: '" + packageToScan + "' for aliases");
}
}
}
...
//省略其它代码
}
然后可以看到注册所有别名的方法 ，registerAliases是怎么做的？
configuration.getTypeAliasRegistry().registerAliases(packageToScan,
typeAliasesSuperType == null ? Object.class : typeAliasesSuperType);
要扫描注册所有的别名之前先要扫描包下面的所有类：
public void registerAliases(String packageName, Class<?> superType) {
ResolverUtil<Class<?>> resolverUtil = new ResolverUtil();
resolverUtil.find(new IsA(superType), packageName);
//通过ResolverUtil获取到的所有类都赋值给一个集合
Set<Class<? extends Class<?>>> typeSet = resolverUtil.getClasses();
/*遍历集合，然后一个个注册*/
Iterator var5 = typeSet.iterator();
while(var5.hasNext()) {
Class<?> type = (Class)var5.next();
if (!type.isAnonymousClass() && !type.isInterface() && !type.isMemberClass()) {
this.registerAlias(type);
}
}
}
ResolverUtil是怎么通过packageName去查找的呢，可以再继续跟一下
public ResolverUtil<T> find(ResolverUtil.Test test, String packageName) {
//获取包路径
String path = this.getPackagePath(packageName);
try {
//VFS类用单例模式实现，先获取集合
List<String> children = VFS.getInstance().list(path);
Iterator var5 = children.iterator();
//遍历,.class文件的选出来
while(var5.hasNext()) {
String child = (String)var5.next();
if (child.endsWith(".class")) {
this.addIfMatching(test, child);
}
}
} catch (IOException var7) {
log.error("Could not read package: " + packageName, var7);
}
return this;
}
获取packPath只是获取一下相对路径
protected String getPackagePath(String packageName) {
return packageName == null ? null : packageName.replace('.', '/');
}
校验方法addIfMatching：
protected void addIfMatching(ResolverUtil.Test test, String fqn) {
try {
String externalName = fqn.substring(0, fqn.indexOf(46)).replace('/', '.');
ClassLoader loader = this.getClassLoader();//类加载器
if (log.isDebugEnabled()) {
log.debug("Checking to see if class " + externalName + " matches criteria [" + test + "]");
}
Class<?> type = loader.loadClass(externalName);//通过类加载器加载类
if (test.matches(type)) {//校验是否符合
this.matches.add(type);
}
} catch (Throwable var6) {
log.warn("Could not examine class '" + fqn + "' due to a " + var6.getClass().getName() + " with message: " + var6.getMessage());
}
}
VFS类具体是怎么setInstance的？继续跟：
//这里的关键点就是getResources，Thread.currentThread().getContextClassLoader().getResources()，其实总结一下Mybatis的类扫描还是要依赖与jdk提供的类加载器
protected static List<URL> getResources(String path) throws IOException {
//获取到资源路径以列表形式放在集合里
return Collections.list(Thread.currentThread().getContextClassLoader().getResources(path));
}
...
public List<String> list(String path) throws IOException {
List<String> names = new ArrayList();
Iterator var3 = getResources(path).iterator();
//遍历封装成列表
while(var3.hasNext()) {
URL url = (URL)var3.next();
names.addAll(this.list(url, path));
}
return names;
}
ok，本博客只是稍微跟一下源码，并没有对Mybatis的源码进行比较系统更高层次的分析。
跟了一下源码知道，稍微总结一下Mybatis对别名的注册是先将从sqlSessionFactoryBean类set的别名报名进行tokenizeToStringArray拆分成数组，然后将包名数组丢给ResolverUtil类和VFS等类进行一系列类加载遍历，之后将 resolverUtil.getClasses()获取的类都赋值给Set<Class>> typeSet 一个集合。其中也是依赖与类加载器。
支持Ant通配符方式setTypeAliasesPackage解决方案
从这个源码比较简单的分析过程，我们并没有找到支持所谓通配符的方法，通过类加载的话也是要传个相对路径去遍历，不过我上面描述的业务场景是要兼容通配符的情况的，一般不会去改包名，假如这个项目有一定规模的话。
下面给出我的解决方案：
package com.muses.taoshop.common.core.database.annotation;
import org.springframework.core.io.support.ResourcePatternResolver;
import org.springframework.util.ClassUtils;
import static com.muses.taoshop.common.core.database.config.BaseConfig.ENTITY_PACKAGES;
public class AnnotationConstants {
public static final String DEFAULT_RESOURCE_PATTERN = "**/*.class";
public final static String PACKAGE_PATTERN =
ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX
+ ClassUtils.convertClassNameToResourcePath(ENTITY_PACKAGES)
+ DEFAULT_RESOURCE_PATTERN;
}
写一个扫描类，代码参考Hibernate的AnnotationSessionFactoryBean源码
package com.muses.taoshop.common.core.database.annotation;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.core.io.support.ResourcePatternResolver;
import java.io.IOException;
import java.util.*;
import org.springframework.core.io.Resource;
import org.springframework.core.type.classreading.CachingMetadataReaderFactory;
import org.springframework.core.type.classreading.MetadataReader;
import org.springframework.core.type.classreading.MetadataReaderFactory;
import org.springframework.stereotype.Component;
import org.springframework.util.CollectionUtils;
import org.thymeleaf.util.StringUtils;
import static com.muses.taoshop.common.core.database.annotation.AnnotationConstants.PACKAGE_PATTERN;
/**
* <pre>
* TypeAlicsesPackage的扫描类
* </pre>
*
* @author nicky
* @version 1.00.00
* <pre>
* 修改记录
* 修改后版本: 修改人： 修改日期: 2018.12.01 18:23 修改内容:
* </pre>
*/
@Component
public class TypeAliasesPackageScanner {
protected final static Logger LOGGER = LoggerFactory.getLogger(TypeAliasesPackageScanner.class);
private static ResourcePatternResolver resourcePatternResolver = new PathMatchingResourcePatternResolver();
/* private TypeFilter[] entityTypeFilters = new TypeFilter[]{new AnnotationTypeFilter(Entity.class, false),
new AnnotationTypeFilter(Embeddable.class, false),
new AnnotationTypeFilter(MappedSuperclass.class, false),
new AnnotationTypeFilter(org.hibernate.annotations.Entity.class, false)};*/
public static String getTypeAliasesPackages() {
Set<String> packageNames = new TreeSet<String>();
//TreeSet packageNames = new TreeSet();
String typeAliasesPackage ="";
try {
//加载所有的资源
Resource[] resources = resourcePatternResolver.getResources(PACKAGE_PATTERN);
MetadataReaderFactory readerFactory = new CachingMetadataReaderFactory(resourcePatternResolver);
//遍历资源
for (Resource resource : resources) {
if (resource.isReadable()) {
MetadataReader reader = readerFactory.getMetadataReader(resource);
String className = reader.getClassMetadata().getClassName();
//eg:com.muses.taoshop.item.entity.ItemBrand
LOGGER.info("className : {} "+className);
try{
//eg:com.muses.taoshop.item.entity
LOGGER.info("packageName : {} "+Class.forName(className).getPackage().getName());
packageNames.add(Class.forName(className).getPackage().getName());
}catch (ClassNotFoundException e){
LOGGER.error("classNotFoundException : {} "+e);
}
}
}
} catch (IOException e) {
LOGGER.error("ioException =>: {} " + e);
}
//集合不为空的情况，拼装一下数据
if (!CollectionUtils.isEmpty(packageNames)) {
typeAliasesPackage = StringUtils.join(packageNames.toArray() , ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS);
}else{
LOGGER.info("set empty,size:{} "+packageNames.size());
}
return typeAliasesPackage;
}
}
然后刚才的Mybatis配置类改一下，主要改 String typeAliasesPackage = packageScanner.getTypeAliasesPackages();通过扫描类去获取一下，重点代码在TypeAliasesPackageScanner 扫描类
package com.muses.taoshop.common.core.database.config;
//省略代码
@MapperScan(
basePackages = MAPPER_PACKAGES,
annotationClass = MybatisRepository.class,
sqlSessionFactoryRef = SQL_SESSION_FACTORY
)
@EnableTransactionManagement
@Configuration
public class MybatisConfig {
//省略其它代码，主要看sqlSessionFactory配置
@Primary
@Bean(name = SQL_SESSION_FACTORY)
public SqlSessionFactory sqlSessionFactory(@Qualifier(DATA_SOURCE_NAME)DataSource dataSource)throws Exception{
//SpringBoot默认使用DefaultVFS进行扫描，但是没有扫描到jar里的实体类
VFS.addImplClass(SpringBootVFS.class);
SqlSessionFactoryBean factoryBean = new SqlSessionFactoryBean();
factoryBean.setDataSource(dataSource);
//factoryBean.setConfigLocation(new ClassPathResource("mybatis-config.xml"));
ResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
try{
factoryBean.setMapperLocations(resolver.getResources("classpath*:/mybatis/*Mapper.xml"));
String typeAliasesPackage = packageScanner.getTypeAliasesPackages();
//设置一下TypeAliasesPackage
factoryBean.setTypeAliasesPackage(typeAliasesPackage);
SqlSessionFactory sqlSessionFactory = factoryBean.getObject();
return sqlSessionFactory;
}catch (Exception e){
e.printStackTrace();
throw new RuntimeException();
}
}