Mybatis源码分析(三)--动态Sql中的参数解析

   //方法
   User findUser(@Param("name") String name,int age,String email)
   //对应xml
<select id="findUser" resultType="cn.mrdear.users.dao.User">
	SELECT * FROM user WHERE username = #{name} AND age = #{age} AND email = #{email} 
</select>
//调用参数
   final User user = userMapper.findUser("quding", 18, "qq@mail.com");

public ParamNameResolver(Configuration config, Method method) {
   final Class<?>[] paramTypes = method.getParameterTypes();//获取参数类型,对于上述例子则是String,int,String
   final Annotation[][] paramAnnotations = method.getParameterAnnotations();//这里获取到的则是@Param,getParameterAnnotations方法也用到了动态代理.
   final SortedMap<Integer, String> map = new TreeMap<Integer, String>();
   int paramCount = paramAnnotations.length;
   // get names from @Param annotations
   for (int paramIndex = 0; paramIndex < paramCount; paramIndex++) {
     if (isSpecialParameter(paramTypes[paramIndex])) { //过滤其内部一些特殊类型
       // skip special parameters
       continue;
     }
     String name = null;
     for (Annotation annotation : paramAnnotations[paramIndex]) {
       if (annotation instanceof Param) {
         hasParamAnnotation = true;
         name = ((Param) annotation).value();//获取到'name'值
         break;
       }
     }
     if (name == null) {
       // @Param was not specified.
       if (config.isUseActualParamName()) {//默认为true,因此编译后参数都是args0,args1之类,因此这里获取的也是args0...
         name = getActualParamName(method, paramIndex);
       }
       //当上面配置为false的时候这里才会使用0,1代替,因此如果未开启则会报错
       if (name == null) {
         // use the parameter index as the name ("0", "1", ...)
         // gcode issue #71
         name = String.valueOf(map.size());//上述都没的话则世界使用map的index.
       }
     }
     map.put(paramIndex, name);
   }
   names = Collections.unmodifiableSortedMap(map);
 }

//mapper接口
  User findUser(@Param("name") String name, @Param("user") User user,@Param("ids") List<Long> ids);
//xml
    <select id="findUser" resultType="cn.mrdear.users.dao.User">
		SELECT * FROM user WHERE username = #{name} AND age = #{user.age} AND email = #{user.email}
		OR id in
		<foreach collection="ids" item="item" open="(" close=")" separator=",">
			#{item}
		</foreach>
	</select>

private Object wrapCollection(final Object object) {
  if (object instanceof Collection) {
    StrictMap<Object> map = new StrictMap<Object>();
    map.put("collection", object);
    if (object instanceof List) {
      map.put("list", object);
    }
    return map;
  } else if (object != null && object.getClass().isArray()) {
    StrictMap<Object> map = new StrictMap<Object>();
    map.put("array", object);
    return map;
  }
  return object;
}

@Override
 public void setParameters(PreparedStatement ps) {
   ErrorContext.instance().activity("setting parameters").object(mappedStatement.getParameterMap().getId());
   List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();
   if (parameterMappings != null) {
       //parameterMappings存储着要设置进去的值类型等信息
     for (int i = 0; i < parameterMappings.size(); i++) {
       ParameterMapping parameterMapping = parameterMappings.get(i);
       if (parameterMapping.getMode() != ParameterMode.OUT) {
         Object value;
         String propertyName = parameterMapping.getProperty();
         //AdditionalParameter是从ContextMap中copy到的,其没有的话说明是_parameter里面的值.
         if (boundSql.hasAdditionalParameter(propertyName)) { // issue #448 ask first for additional params
           value = boundSql.getAdditionalParameter(propertyName);
         } else if (parameterObject == null) {
           value = null;
         } else if (typeHandlerRegistry.hasTypeHandler(parameterObject.getClass())) {
           value = parameterObject;
         } else {
             //获取_parameter里面的值.
           MetaObject metaObject = configuration.newMetaObject(parameterObject);
           //其内部是一个递归实现获取.
           value = metaObject.getValue(propertyName);
         }
           //typeHandle的处理
         TypeHandler typeHandler = parameterMapping.getTypeHandler();
         JdbcType jdbcType = parameterMapping.getJdbcType();
         if (value == null && jdbcType == null) {
           jdbcType = configuration.getJdbcTypeForNull();
         }
         try {
           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);
         }
       }
     }
   }
 }

public Object getValue(String name) {
  PropertyTokenizer prop = new PropertyTokenizer(name);
  //hasNext判断user.username这种类型
  if (prop.hasNext()) {
    MetaObject metaValue = metaObjectForProperty(prop.getIndexedName());
    if (metaValue == SystemMetaObject.NULL_META_OBJECT) {
      return null;
    } else {
        //递归获取
      return metaValue.getValue(prop.getChildren());
    }
  } else {
    return objectWrapper.get(prop);
  }
}