MyBatis配置文件详解

Mybatis配置文件

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>

    <!-- 指定properties配置文件， 我这里面配置的是数据库相关 -->
    <properties resource="dbConfig.properties">
        <property name="dialect" value="mysql"/>
        <property name="pageSqlId" value=".*page$"/>
    </properties>

    <!-- 指定Mybatis使用log4j -->
    <settings>
        <setting name="logImpl" value="LOG4J"/>
        <setting name="cacheEnabled" value="true"/>
    </settings>

    <!--配置别名-->
    <typeAliases>
        <typeAlias alias="student" type="mybatis.core.Student"/>
    </typeAliases>

    <typeHandlers>
        <typeHandler javaType="list" jdbcType="VARCHAR"
                     handler="mybatis.typeHandler.ListTypeHandler"/>
    </typeHandlers>

    <plugins>
        <plugin interceptor="mybatis.plugin.PageHelper"></plugin>
    </plugins>

    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/student"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>


    <!-- 映射文件，mybatis精髓， 后面才会细讲 -->
    <mappers>
        <mapper resource="userDao-mapping.xml"/>
    </mappers>

</configuration>

MyBatis配置文件解析源码

 //Resources.getResourceAsReader(resource)获得read后，调用build()方法
 sessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsReader(resource));

 //接下来我们看build()方法
 public SqlSessionFactory build(Reader reader) {
    return build(reader, null, null);
 }

 public SqlSessionFactory build(Reader reader, String environment, Properties properties) {
    try {
      XMLConfigBuilder parser = new XMLConfigBuilder(reader, environment, properties);
      return build(parser.parse());
    } catch (Exception e) {
      throw ExceptionFactory.wrapException("Error building SqlSession.", e);
    } finally {
      ErrorContext.instance().reset();
      try {
        reader.close();
      } catch (IOException e) {
        // Intentionally ignore. Prefer previous error.
      }
    }
  }

 public Configuration parse() {
    if (parsed) {
      throw new BuilderException("Each XMLConfigBuilder can only be used once.");
    }
    parsed = true;
    //configuration作为根节点开始解析
    parseConfiguration(parser.evalNode("/configuration"));
    return configuration;
  }

  //分别解析configuration的10个子节点
  private void parseConfiguration(XNode root) {
    try {
      propertiesElement(root.evalNode("properties")); //issue #117 read properties first
      typeAliasesElement(root.evalNode("typeAliases"));
      pluginElement(root.evalNode("plugins"));
      objectFactoryElement(root.evalNode("objectFactory"));
      objectWrapperFactoryElement(root.evalNode("objectWrapperFactory"));
      settingsElement(root.evalNode("settings"));
      environmentsElement(root.evalNode("environments")); // read it after objectFactory and objectWrapperFactory issue #631
      databaseIdProviderElement(root.evalNode("databaseIdProvider"));
      typeHandlerElement(root.evalNode("typeHandlers"));
      mapperElement(root.evalNode("mappers"));
    } catch (Exception e) {
      throw new BuilderException("Error parsing SQL Mapper Configuration. Cause: " + e, e);
    }
  }

配置文件解析之properties

开发过程中，为了方便修改数据库的信息，我们将数据库的配置放在配置文件中。如下：
password=qa，然后添加配置<property name="password" value="${password}"/>
即可。

源码片段

private void propertiesElement(XNode context) throws Exception {
    if (context != null) {
      Properties defaults = context.getChildrenAsProperties();
      String resource = context.getStringAttribute("resource");
      String url = context.getStringAttribute("url");
      //resource和url不能同时指定
      if (resource != null && url != null) {
        throw new BuilderException("The properties element cannot specify both a URL and a resource based property file reference.  Please specify one or the other.");
      }
      if (resource != null) {
        defaults.putAll(Resources.getResourceAsProperties(resource));
      } else if (url != null) {
        defaults.putAll(Resources.getUrlAsProperties(url));
      }
      //使用Java代码直接配置
      Properties vars = configuration.getVariables();
      if (vars != null) {
        defaults.putAll(vars);
      }
      //set到parser
      parser.setVariables(defaults);
      //set到configuration
      configuration.setVariables(defaults);
    }
  }

配置文件解析之environments

开发过程中，开发环境的数据库用户名、密码一定和线上的不一样，配置environments便可以随意切换数据库。

源码片段

private void environmentsElement(XNode context) throws Exception {
    if (context != null) {
      if (environment == null) {
        //获取默认environment
        environment = context.getStringAttribute("default");
      }
      for (XNode child : context.getChildren()) {
        String id = child.getStringAttribute("id");
        //若果是默认的environment变进行如下设置
        if (isSpecifiedEnvironment(id)) {
          //事务， mybatis有两种：JDBC 和 MANAGED, 配置为JDBC则直接使用JDBC的事务，配置为MANAGED则是将事务托管给容器， 
          TransactionFactory txFactory = transactionManagerElement(child.evalNode("transactionManager"));
          DataSourceFactory dsFactory = dataSourceElement(child.evalNode("dataSource"));
          DataSource dataSource = dsFactory.getDataSource();
          Environment.Builder environmentBuilder = new Environment.Builder(id)
              .transactionFactory(txFactory)
              .dataSource(dataSource);
          //set到configuration
          configuration.setEnvironment(environmentBuilder.build());
        }
      }
    }
  }

配置文件解析之typeAliases

通过别名配置，我们不需要写出完整的包名。比如我们配置了<typeAliases><typeAlias alias="student" type="mybatis.core.Student"/></typeAliases>，我们在*.mapping.xml只需要写student即可，<select id="findStudentById" useCache="true" resultType="student">select * from student where id = #{id}</select>

配置别名的方式

1.  <typeAliases><typeAlias alias="student" type="mybatis.core.Student"/></typeAliases>

2.  <typeAliases><package name="mybatis.core"></package></typeAliases>
    在mybatis.core包下的Student类中，添加@Alias("student")

源码片段

  private void typeAliasesElement(XNode parent) {
    if (parent != null) {
      for (XNode child : parent.getChildren()) {
        //如果子节点是package, 那么就获取package节点的name属性， mybatis会扫描指定的package
        if ("package".equals(child.getName())) {
          String typeAliasPackage = child.getStringAttribute("name");
          //注册别名
          configuration.getTypeAliasRegistry().registerAliases(typeAliasPackage);
        } else {
          //如果子节点是typeAlias节点，那么就获取alias属性和type的属性值
          String alias = child.getStringAttribute("alias");
          String type = child.getStringAttribute("type");
          try {
            Class<?> clazz = Resources.classForName(type);
            if (alias == null) {
              typeAliasRegistry.registerAlias(clazz);
            } else {
              typeAliasRegistry.registerAlias(alias, clazz);
            }
          } catch (ClassNotFoundException e) {
            throw new BuilderException("Error registering typeAlias for '" + alias + "'. Cause: " + e, e);
          }
        }
      }
    }
  }

 /*
 *    Copyright 2009-2013 the original author or authors.
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the License.
 *    You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 */
package org.apache.ibatis.type;

import java.math.BigDecimal;
import java.math.BigInteger;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Date;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Set;

import org.apache.ibatis.io.ResolverUtil;
import org.apache.ibatis.io.Resources;

/**
 * @author Clinton Begin
 */
public class TypeAliasRegistry {

  private final Map<String, Class<?>> TYPE_ALIASES = new HashMap<String, Class<?>>();

  //MyBatis默认为我们注册的别名
  public TypeAliasRegistry() {
    registerAlias("string", String.class);

    registerAlias("byte", Byte.class);
    registerAlias("long", Long.class);
    registerAlias("short", Short.class);
    registerAlias("int", Integer.class);
    registerAlias("integer", Integer.class);
    registerAlias("double", Double.class);
    registerAlias("float", Float.class);
    registerAlias("boolean", Boolean.class);

    registerAlias("byte[]", Byte[].class);
    registerAlias("long[]", Long[].class);
    registerAlias("short[]", Short[].class);
    registerAlias("int[]", Integer[].class);
    registerAlias("integer[]", Integer[].class);
    registerAlias("double[]", Double[].class);
    registerAlias("float[]", Float[].class);
    registerAlias("boolean[]", Boolean[].class);

    registerAlias("_byte", byte.class);
    registerAlias("_long", long.class);
    registerAlias("_short", short.class);
    registerAlias("_int", int.class);
    registerAlias("_integer", int.class);
    registerAlias("_double", double.class);
    registerAlias("_float", float.class);
    registerAlias("_boolean", boolean.class);

    registerAlias("_byte[]", byte[].class);
    registerAlias("_long[]", long[].class);
    registerAlias("_short[]", short[].class);
    registerAlias("_int[]", int[].class);
    registerAlias("_integer[]", int[].class);
    registerAlias("_double[]", double[].class);
    registerAlias("_float[]", float[].class);
    registerAlias("_boolean[]", boolean[].class);

    registerAlias("date", Date.class);
    registerAlias("decimal", BigDecimal.class);
    registerAlias("bigdecimal", BigDecimal.class);
    registerAlias("biginteger", BigInteger.class);
    registerAlias("object", Object.class);

    registerAlias("date[]", Date[].class);
    registerAlias("decimal[]", BigDecimal[].class);
    registerAlias("bigdecimal[]", BigDecimal[].class);
    registerAlias("biginteger[]", BigInteger[].class);
    registerAlias("object[]", Object[].class);

    registerAlias("map", Map.class);
    registerAlias("hashmap", HashMap.class);
    registerAlias("list", List.class);
    registerAlias("arraylist", ArrayList.class);
    registerAlias("collection", Collection.class);
    registerAlias("iterator", Iterator.class);

    registerAlias("ResultSet", ResultSet.class);
  }

  @SuppressWarnings("unchecked")
  // throws class cast exception as well if types cannot be assigned
  public <T> Class<T> resolveAlias(String string) {
    try {
      if (string == null) return null;
      String key = string.toLowerCase(Locale.ENGLISH); // issue #748
      Class<T> value;
      if (TYPE_ALIASES.containsKey(key)) {
        value = (Class<T>) TYPE_ALIASES.get(key);
      } else {
        value = (Class<T>) Resources.classForName(string);
      }
      return value;
    } catch (ClassNotFoundException e) {
      throw new TypeException("Could not resolve type alias '" + string + "'.  Cause: " + e, e);
    }
  }

  //package方式配置，注册别名
  public void registerAliases(String packageName){
    registerAliases(packageName, Object.class);
  }
  //扫描获取package下的类
  public void registerAliases(String packageName, Class<?> superType){
    ResolverUtil<Class<?>> resolverUtil = new ResolverUtil<Class<?>>();
    resolverUtil.find(new ResolverUtil.IsA(superType), packageName);
    Set<Class<? extends Class<?>>> typeSet = resolverUtil.getClasses();
    for(Class<?> type : typeSet){
      // Ignore inner classes and interfaces (including package-info.java)
      // Skip also inner classes. See issue #6
      if (!type.isAnonymousClass() && !type.isInterface() && !type.isMemberClass()) {
        registerAlias(type);
      }
    }
  }
  //获取bean的注解，注解值作为别名
  public void registerAlias(Class<?> type) {
    String alias = type.getSimpleName();
    Alias aliasAnnotation = type.getAnnotation(Alias.class);
    if (aliasAnnotation != null) {
      alias = aliasAnnotation.value();
    } 
    registerAlias(alias, type);
  }
  //使用map来保存别名
  public void registerAlias(String alias, Class<?> value) {
    if (alias == null) throw new TypeException("The parameter alias cannot be null");
    String key = alias.toLowerCase(Locale.ENGLISH); // issue #748
    if (TYPE_ALIASES.containsKey(key) && TYPE_ALIASES.get(key) != null && !TYPE_ALIASES.get(key).equals(value)) {
      throw new TypeException("The alias '" + alias + "' is already mapped to the value '" + TYPE_ALIASES.get(key).getName() + "'.");
    }
    TYPE_ALIASES.put(key, value);
  }

  public void registerAlias(String alias, String value) {
    try {
      registerAlias(alias, Resources.classForName(value));
    } catch (ClassNotFoundException e) {
      throw new TypeException("Error registering type alias "+alias+" for "+value+". Cause: " + e, e);
    }
  }
  
  /**
   * @since 3.2.2
   */
  public Map<String, Class<?>> getTypeAliases() {
    return Collections.unmodifiableMap(TYPE_ALIASES);
  }

}


###Mybatis配置文件

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>

<!-- 指定properties配置文件， 我这里面配置的是数据库相关 -->
<properties resource="dbConfig.properties">
    <property name="dialect" value="mysql"/>
    <property name="pageSqlId" value=".*page$"/>
</properties>

<!-- 指定Mybatis使用log4j -->
<settings>
    <setting name="logImpl" value="LOG4J"/>
    <setting name="cacheEnabled" value="true"/>
</settings>

<!--配置别名-->
<typeAliases>
    <typeAlias alias="student" type="mybatis.core.Student"/>
</typeAliases>

<typeHandlers>
    <typeHandler javaType="list" jdbcType="VARCHAR"
                 handler="mybatis.typeHandler.ListTypeHandler"/>
</typeHandlers>

<plugins>
    <plugin interceptor="mybatis.plugin.PageHelper"></plugin>
</plugins>

<environments default="development">
    <environment id="development">
        <transactionManager type="JDBC"/>
        <dataSource type="POOLED">
            <property name="driver" value="com.mysql.jdbc.Driver"/>
            <property name="url" value="jdbc:mysql://localhost:3306/student"/>
            <property name="username" value="root"/>
            <property name="password" value="root"/>
        </dataSource>
    </environment>
</environments>


<!-- 映射文件，mybatis精髓， 后面才会细讲 -->
<mappers>
    <mapper resource="userDao-mapping.xml"/>
</mappers>

</configuration>

###MyBatis配置文件解析源码

//Resources.getResourceAsReader(resource)获得read后，调用build()方法
sessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsReader(resource));

//接下来我们看build()方法
public SqlSessionFactory build(Reader reader) {
return build(reader, null, null);
}

public SqlSessionFactory build(Reader reader, String environment, Properties properties) {
try {
XMLConfigBuilder parser = new XMLConfigBuilder(reader, environment, properties);
return build(parser.parse());
} catch (Exception e) {
throw ExceptionFactory.wrapException("Error building SqlSession.", e);
} finally {
ErrorContext.instance().reset();
try {
reader.close();
} catch (IOException e) {
// Intentionally ignore. Prefer previous error.
}
}
}

public Configuration parse() {
if (parsed) {
throw new BuilderException("Each XMLConfigBuilder can only be used once.");
}
parsed = true;
//configuration作为根节点开始解析
parseConfiguration(parser.evalNode("/configuration"));
return configuration;
}

//分别解析configuration的10个子节点
private void parseConfiguration(XNode root) {
try {
propertiesElement(root.evalNode("properties")); //issue #117 read properties first
typeAliasesElement(root.evalNode("typeAliases"));
pluginElement(root.evalNode("plugins"));
objectFactoryElement(root.evalNode("objectFactory"));
objectWrapperFactoryElement(root.evalNode("objectWrapperFactory"));
settingsElement(root.evalNode("settings"));
environmentsElement(root.evalNode("environments")); // read it after objectFactory and objectWrapperFactory issue #631
databaseIdProviderElement(root.evalNode("databaseIdProvider"));
typeHandlerElement(root.evalNode("typeHandlers"));
mapperElement(root.evalNode("mappers"));
} catch (Exception e) {
throw new BuilderException("Error parsing SQL Mapper Configuration. Cause: " + e, e);
}
}

###配置文件解析之properties
>开发过程中，为了方便修改数据库的信息，我们将数据库的配置放在配置文件中。如下：
password=qa，然后添加配置<property name="password" value="${password}"/>
即可。

####源码片段

private void propertiesElement(XNode context) throws Exception {
if (context != null) {
Properties defaults = context.getChildrenAsProperties();
String resource = context.getStringAttribute("resource");
String url = context.getStringAttribute("url");
//resource和url不能同时指定
if (resource != null && url != null) {
throw new BuilderException("The properties element cannot specify both a URL and a resource based property file reference. Please specify one or the other.");
}
if (resource != null) {
defaults.putAll(Resources.getResourceAsProperties(resource));
} else if (url != null) {
defaults.putAll(Resources.getUrlAsProperties(url));
}
//使用Java代码直接配置
Properties vars = configuration.getVariables();
if (vars != null) {
defaults.putAll(vars);
}
//set到parser
parser.setVariables(defaults);
//set到configuration
configuration.setVariables(defaults);
}
}

###配置文件解析之environments
>开发过程中，开发环境的数据库用户名、密码一定和线上的不一样，配置environments便可以随意切换数据库。

####源码片段

private void environmentsElement(XNode context) throws Exception {
if (context != null) {
if (environment == null) {
//获取默认environment
environment = context.getStringAttribute("default");
}
for (XNode child : context.getChildren()) {
String id = child.getStringAttribute("id");
//若果是默认的environment变进行如下设置
if (isSpecifiedEnvironment(id)) {
//事务， mybatis有两种：JDBC 和 MANAGED, 配置为JDBC则直接使用JDBC的事务，配置为MANAGED则是将事务托管给容器，
TransactionFactory txFactory = transactionManagerElement(child.evalNode("transactionManager"));
DataSourceFactory dsFactory = dataSourceElement(child.evalNode("dataSource"));
DataSource dataSource = dsFactory.getDataSource();
Environment.Builder environmentBuilder = new Environment.Builder(id)
.transactionFactory(txFactory)
.dataSource(dataSource);
//set到configuration
configuration.setEnvironment(environmentBuilder.build());
}
}
}
}

###配置文件解析之typeAliases
>通过别名配置，我们不需要写出完整的包名。比如我们配置了<typeAliases><typeAlias alias="student" type="mybatis.core.Student"/></typeAliases>，我们在*.mapping.xml只需要写student即可，<select id="findStudentById" useCache="true" resultType="student">select * from student where id = #{id}</select>

####配置别名的方式

  1. <typeAliases><typeAlias alias="student" type="mybatis.core.Student"/></typeAliases>

  2. <typeAliases><package name="mybatis.core"></package></typeAliases>
    在mybatis.core包下的Student类中，添加@Alias("student")


####源码片段

private void typeAliasesElement(XNode parent) {
if (parent != null) {
for (XNode child : parent.getChildren()) {
//如果子节点是package, 那么就获取package节点的name属性， mybatis会扫描指定的package
if ("package".equals(child.getName())) {
String typeAliasPackage = child.getStringAttribute("name");
//注册别名
configuration.getTypeAliasRegistry().registerAliases(typeAliasPackage);
} else {
//如果子节点是typeAlias节点，那么就获取alias属性和type的属性值
String alias = child.getStringAttribute("alias");
String type = child.getStringAttribute("type");
try {
Class<?> clazz = Resources.classForName(type);
if (alias == null) {
typeAliasRegistry.registerAlias(clazz);
} else {
typeAliasRegistry.registerAlias(alias, clazz);
}
} catch (ClassNotFoundException e) {
throw new BuilderException("Error registering typeAlias for '" + alias + "'. Cause: " + e, e);
}
}
}
}
}

/*

  • Copyright 2009-2013 the original author or authors.
  • Licensed under the Apache License, Version 2.0 (the "License");
  • you may not use this file except in compliance with the License.
  • You may obtain a copy of the License at
  •   http://www.apache.org/licenses/LICENSE-2.0
  • Unless required by applicable law or agreed to in writing, software
  • distributed under the License is distributed on an "AS IS" BASIS,
  • WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  • See the License for the specific language governing permissions and
  • limitations under the License.
    */
    package org.apache.ibatis.type;

import java.math.BigDecimal;
import java.math.BigInteger;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Date;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Set;

import org.apache.ibatis.io.ResolverUtil;
import org.apache.ibatis.io.Resources;

/**

  • @author Clinton Begin
    */
    public class TypeAliasRegistry {

private final Map<String, Class<?>> TYPE_ALIASES = new HashMap<String, Class<?>>();

//MyBatis默认为我们注册的别名
public TypeAliasRegistry() {
registerAlias("string", String.class);

registerAlias("byte", Byte.class);
registerAlias("long", Long.class);
registerAlias("short", Short.class);
registerAlias("int", Integer.class);
registerAlias("integer", Integer.class);
registerAlias("double", Double.class);
registerAlias("float", Float.class);
registerAlias("boolean", Boolean.class);

registerAlias("byte[]", Byte[].class);
registerAlias("long[]", Long[].class);
registerAlias("short[]", Short[].class);
registerAlias("int[]", Integer[].class);
registerAlias("integer[]", Integer[].class);
registerAlias("double[]", Double[].class);
registerAlias("float[]", Float[].class);
registerAlias("boolean[]", Boolean[].class);

registerAlias("_byte", byte.class);
registerAlias("_long", long.class);
registerAlias("_short", short.class);
registerAlias("_int", int.class);
registerAlias("_integer", int.class);
registerAlias("_double", double.class);
registerAlias("_float", float.class);
registerAlias("_boolean", boolean.class);

registerAlias("_byte[]", byte[].class);
registerAlias("_long[]", long[].class);
registerAlias("_short[]", short[].class);
registerAlias("_int[]", int[].class);
registerAlias("_integer[]", int[].class);
registerAlias("_double[]", double[].class);
registerAlias("_float[]", float[].class);
registerAlias("_boolean[]", boolean[].class);

registerAlias("date", Date.class);
registerAlias("decimal", BigDecimal.class);
registerAlias("bigdecimal", BigDecimal.class);
registerAlias("biginteger", BigInteger.class);
registerAlias("object", Object.class);

registerAlias("date[]", Date[].class);
registerAlias("decimal[]", BigDecimal[].class);
registerAlias("bigdecimal[]", BigDecimal[].class);
registerAlias("biginteger[]", BigInteger[].class);
registerAlias("object[]", Object[].class);

registerAlias("map", Map.class);
registerAlias("hashmap", HashMap.class);
registerAlias("list", List.class);
registerAlias("arraylist", ArrayList.class);
registerAlias("collection", Collection.class);
registerAlias("iterator", Iterator.class);

registerAlias("ResultSet", ResultSet.class);

}

@SuppressWarnings("unchecked")
// throws class cast exception as well if types cannot be assigned
public <T> Class<T> resolveAlias(String string) {
try {
if (string == null) return null;
String key = string.toLowerCase(Locale.ENGLISH); // issue #748
Class<T> value;
if (TYPE_ALIASES.containsKey(key)) {
value = (Class<T>) TYPE_ALIASES.get(key);
} else {
value = (Class<T>) Resources.classForName(string);
}
return value;
} catch (ClassNotFoundException e) {
throw new TypeException("Could not resolve type alias '" + string + "'. Cause: " + e, e);
}
}

//package方式配置，注册别名
public void registerAliases(String packageName){
registerAliases(packageName, Object.class);
}
//扫描获取package下的类
public void registerAliases(String packageName, Class<?> superType){
ResolverUtil<Class<?>> resolverUtil = new ResolverUtil<Class<?>>();
resolverUtil.find(new ResolverUtil.IsA(superType), packageName);
Set<Class<? extends Class<?>>> typeSet = resolverUtil.getClasses();
for(Class<?> type : typeSet){
// Ignore inner classes and interfaces (including package-info.java)
// Skip also inner classes. See issue #6
if (!type.isAnonymousClass() && !type.isInterface() && !type.isMemberClass()) {
registerAlias(type);
}
}
}
//获取bean的注解，注解值作为别名
public void registerAlias(Class<?> type) {
String alias = type.getSimpleName();
Alias aliasAnnotation = type.getAnnotation(Alias.class);
if (aliasAnnotation != null) {
alias = aliasAnnotation.value();
}
registerAlias(alias, type);
}
//使用map来保留别名
public void registerAlias(String alias, Class<?> value) {
if (alias == null) throw new TypeException("The parameter alias cannot be null");
String key = alias.toLowerCase(Locale.ENGLISH); // issue #748
if (TYPE_ALIASES.containsKey(key) && TYPE_ALIASES.get(key) != null && !TYPE_ALIASES.get(key).equals(value)) {
throw new TypeException("The alias '" + alias + "' is already mapped to the value '" + TYPE_ALIASES.get(key).getName() + "'.");
}
TYPE_ALIASES.put(key, value);
}

public void registerAlias(String alias, String value) {
try {
registerAlias(alias, Resources.classForName(value));
} catch (ClassNotFoundException e) {
throw new TypeException("Error registering type alias "+alias+" for "+value+". Cause: " + e, e);
}
}

/**

  • @since 3.2.2
    */
    public Map<String, Class<?>> getTypeAliases() {
    return Collections.unmodifiableMap(TYPE_ALIASES);
    }

}

获取别名

public class TypeAliasesTest {    @Test    public void getAliases() {        SqlSessionFactory sqlSessionFactory = MybatisUtil.getSessionFactory();        Configuration con = sqlSessionFactory.getConfiguration();        Map<String, Class<?>> typeMap = con.getTypeAliasRegistry().getTypeAliases();        for (Map.Entry<String, Class<?>> entry : typeMap.entrySet()) {            System.out.println(entry.getKey() + " ================> " + entry.getValue().getSimpleName());        }    }}
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