BaseBuilder.java

/*
 *    Copyright 2009-2012 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.builder;

import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;
import java.util.regex.Pattern;

import org.apache.ibatis.mapping.ParameterMode;
import org.apache.ibatis.mapping.ResultSetType;
import org.apache.ibatis.session.Configuration;
import org.apache.ibatis.type.JdbcType;
import org.apache.ibatis.type.TypeAliasRegistry;
import org.apache.ibatis.type.TypeHandler;
import org.apache.ibatis.type.TypeHandlerRegistry;

/**
 * @author Clinton Begin
 */
/**
 * 构建器的基类，建造者模式
 *
 */
public abstract class BaseBuilder {
  //需要配置，类型别名注册，类型处理器注册3个东西
  protected final Configuration configuration;
  protected final TypeAliasRegistry typeAliasRegistry;
  protected final TypeHandlerRegistry typeHandlerRegistry;

  public BaseBuilder(Configuration configuration) {
    this.configuration = configuration;
    this.typeAliasRegistry = this.configuration.getTypeAliasRegistry();
    this.typeHandlerRegistry = this.configuration.getTypeHandlerRegistry();
  }

  public Configuration getConfiguration() {
    return configuration;
  }

  protected Pattern parseExpression(String regex, String defaultValue) {
    return Pattern.compile(regex == null ? defaultValue : regex);
  }

  protected Boolean booleanValueOf(String value, Boolean defaultValue) {
    return value == null ? defaultValue : Boolean.valueOf(value);
  }

  protected Integer integerValueOf(String value, Integer defaultValue) {
    return value == null ? defaultValue : Integer.valueOf(value);
  }

  //把以逗号分割的一个字符串重新包装，返回一个Set
  protected Set<String> stringSetValueOf(String value, String defaultValue) {
    value = (value == null ? defaultValue : value);
    return new HashSet<String>(Arrays.asList(value.split(",")));
  }

  //解析JdbcType
  protected JdbcType resolveJdbcType(String alias) {
    if (alias == null) {
      return null;
    }
    try {
      return JdbcType.valueOf(alias);
    } catch (IllegalArgumentException e) {
      throw new BuilderException("Error resolving JdbcType. Cause: " + e, e);
    }
  }

  //解析ResultSetType
  protected ResultSetType resolveResultSetType(String alias) {
    if (alias == null) {
      return null;
    }
    try {
      return ResultSetType.valueOf(alias);
    } catch (IllegalArgumentException e) {
      throw new BuilderException("Error resolving ResultSetType. Cause: " + e, e);
    }
  }

  //解析ParameterMode(SP的IN/OUT/INOUT)
  protected ParameterMode resolveParameterMode(String alias) {
    if (alias == null) {
      return null;
    }
    try {
      return ParameterMode.valueOf(alias);
    } catch (IllegalArgumentException e) {
      throw new BuilderException("Error resolving ParameterMode. Cause: " + e, e);
    }
  }

  //根据别名解析Class，然后创建实例
  protected Object createInstance(String alias) {
    Class<?> clazz = resolveClass(alias);
    if (clazz == null) {
      return null;
    }
    try {
      return resolveClass(alias).newInstance();
    } catch (Exception e) {
      throw new BuilderException("Error creating instance. Cause: " + e, e);
    }
  }

  //根据别名解析Class,其实是去查看 类型别名注册/事务管理器别名
  protected Class<?> resolveClass(String alias) {
    if (alias == null) {
      return null;
    }
    try {
      return resolveAlias(alias);
    } catch (Exception e) {
      throw new BuilderException("Error resolving class. Cause: " + e, e);
    }
  }

  //解析类型处理器
  protected TypeHandler<?> resolveTypeHandler(Class<?> javaType, String typeHandlerAlias) {
    if (typeHandlerAlias == null) {
      return null;
    }
    //先取得别名所属的Class
    Class<?> type = resolveClass(typeHandlerAlias);
    //如果不是TypeHandler的子类,报错
    if (type != null && !TypeHandler.class.isAssignableFrom(type)) {
      throw new BuilderException("Type " + type.getName() + " is not a valid TypeHandler because it does not implement TypeHandler interface");
    }
    @SuppressWarnings( "unchecked" ) // already verified it is a TypeHandler
    Class<? extends TypeHandler<?>> typeHandlerType = (Class<? extends TypeHandler<?>>) type;
    //再去调用另一个重载的方法
    return resolveTypeHandler(javaType, typeHandlerType);
  }

  protected TypeHandler<?> resolveTypeHandler(Class<?> javaType, Class<? extends TypeHandler<?>> typeHandlerType) {
    if (typeHandlerType == null) {
      return null;
    }
    // javaType ignored for injected handlers see issue #746 for full detail
    //去typeHandlerRegistry查询对应的TypeHandler
    TypeHandler<?> handler = typeHandlerRegistry.getMappingTypeHandler(typeHandlerType);
    if (handler == null) {
      // not in registry, create a new one
        //如果没有在Registry找到，调用typeHandlerRegistry.getInstance来new一个TypeHandler返回
      handler = typeHandlerRegistry.getInstance(javaType, typeHandlerType);
    }
    return handler;
  }

  protected Class<?> resolveAlias(String alias) {
    return typeAliasRegistry.resolveAlias(alias);
  }
}