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Method of fast database query in complicated environment.
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/*
 * Copyright (c) 2016-2088, fastquery.org and/or its affiliates. All rights reserved.
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.
 *
 * For more information, please see http://www.fastquery.org/.
 *
 */

package org.fastquery.core;

import lombok.Getter;
import org.apache.commons.lang3.ArrayUtils;
import org.fastquery.util.BeanUtil;

import java.lang.reflect.Field;
import java.util.List;
import java.util.Objects;

/**
 * @author xixifeng ([email protected])
 */
public class SelectField
{

    @Getter
    private final Class clazz;
    private final boolean contain;
    private String[] fields = {};

    public SelectField(Class clazz, boolean contain, String... fields)
    {
        Objects.requireNonNull(clazz, "clazz 不能为null");
        this.clazz = clazz;
        this.contain = contain;
        if (fields != null)
        {
            this.fields = fields;
        }
    }

    public String getFields()
    {
        List fieldList = BeanUtil.mapFields(this.clazz);
        StringBuilder sb = new StringBuilder(6 * fieldList.size()); // 一个 field 大概包含 6 个字符
        fieldList.forEach(f -> {
            String fieldName = f.getName();
            if (contain)
            {
                if (this.fields.length == 0 || ArrayUtils.contains(this.fields, fieldName))
                {
                    sb.append(',');
                    sb.append(f.getName());
                }
            }
            else
            {
                if (this.fields.length == 0 || !ArrayUtils.contains(this.fields, fieldName))
                {
                    sb.append(',');
                    sb.append(f.getName());
                }
            }
        });
        int len = sb.length();
        if (len > 0)
        {
            sb.deleteCharAt(0);
        }
        else
        {
            sb.append(1);
        }

        return sb.toString();
    }
}