package org.apache.ibatis.executor.parameter;  

import java.sql.PreparedStatement;

import java.sql.SQLException;  

/**

 * A parameter handler sets the parameters of the {@code PreparedStatement}

 *

 * @author Clinton Begin

 */

public interface ParameterHandler {  

  Object getParameterObject();  

  void setParameters(PreparedStatement ps)

      throws SQLException;  

}

package org.apache.ibatis.scripting.defaults;  

import java.sql.PreparedStatement;

import java.sql.SQLException;

import java.util.List;  

import org.apache.ibatis.executor.ErrorContext;

import org.apache.ibatis.executor.parameter.ParameterHandler;

import org.apache.ibatis.mapping.BoundSql;

import org.apache.ibatis.mapping.MappedStatement;

import org.apache.ibatis.mapping.ParameterMapping;

import org.apache.ibatis.mapping.ParameterMode;

import org.apache.ibatis.reflection.MetaObject;

import org.apache.ibatis.session.Configuration;

import org.apache.ibatis.type.JdbcType;

import org.apache.ibatis.type.TypeException;

import org.apache.ibatis.type.TypeHandler;

import org.apache.ibatis.type.TypeHandlerRegistry;  

/**

 * @author Clinton Begin

 * @author Eduardo Macarron

 */

public class DefaultParameterHandler implements ParameterHandler {  

  private final TypeHandlerRegistry typeHandlerRegistry;  

  private final MappedStatement mappedStatement;

  private final Object parameterObject;  //所有的参数值

  private BoundSql boundSql;

  private Configuration configuration;  

  public DefaultParameterHandler(MappedStatement mappedStatement, Object parameterObject, BoundSql boundSql) {

    this.mappedStatement = mappedStatement;

    this.configuration = mappedStatement.getConfiguration();

    this.typeHandlerRegistry = mappedStatement.getConfiguration().getTypeHandlerRegistry();

    this.parameterObject = parameterObject;

    this.boundSql = boundSql;

  }  

  @Override

  public Object getParameterObject() {

    return parameterObject;

  }  

  @Override

  public void setParameters(PreparedStatement ps) {

    ErrorContext.instance().activity("setting parameters").object(mappedStatement.getParameterMap().getId());

    //获取所有参数，ParameterMapping是java类型和jdbc类型的对应关系

    List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();

    if (parameterMappings != null) {

      for (int i = 0; i < parameterMappings.size(); i++) {

        ParameterMapping parameterMapping = parameterMappings.get(i);

        if (parameterMapping.getMode() != ParameterMode.OUT) {

          //参数值

          Object value;

          //获取参数名称

          String propertyName = parameterMapping.getProperty();

          if (boundSql.hasAdditionalParameter(propertyName)) { // issue #448 ask first for additional params

            //获取参数值

            value = boundSql.getAdditionalParameter(propertyName);

          } else if (parameterObject == null) {

            value = null;

          } else if (typeHandlerRegistry.hasTypeHandler(parameterObject.getClass()))

            //如果是单个值则直接赋值

            value = parameterObject;

          } else {

            MetaObject metaObject = configuration.newMetaObject(parameterObject);

            value = metaObject.getValue(propertyName);

          }

          //获取参数值对应的jdbc类型

          TypeHandler typeHandler = parameterMapping.getTypeHandler();

          JdbcType jdbcType = parameterMapping.getJdbcType();

          if (value == null && jdbcType == null) {

            jdbcType = configuration.getJdbcTypeForNull();

          }

          try {

            //设置参数值和jdbc类型的对应关系

            typeHandler.setParameter(ps, i + 1, value, jdbcType);

          } catch (TypeException e) {

            throw new TypeException("Could not set parameters for mapping: " + parameterMapping + ". Cause: " + e, e);

          } catch (SQLException e) {

            throw new TypeException("Could not set parameters for mapping: " + parameterMapping + ". Cause: " + e, e);

          }

        }

      }

    }

  }  

}