java读取大文件oom_java中如何读取文件

package com.example.demo;

import com.alibaba.fastjson.JSON;
import com.example.demo.entity.Entity;
import org.apache.commons.io.FileUtils;
import org.apache.commons.io.LineIterator;
import org.elasticsearch.action.bulk.BulkRequest;
import org.elasticsearch.action.index.IndexRequest;
import org.elasticsearch.action.index.IndexResponse;
import org.elasticsearch.client.RequestOptions;
import org.elasticsearch.client.RestHighLevelClient;
import org.elasticsearch.common.xcontent.XContentType;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.test.context.SpringBootTest;

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import java.util.Objects;

/**
 * 读取大文件
 * csv格式
 *
 * @author lhb
 * @date 2021/11/11
 * @since 1.0.0
 */
@SpringBootTest
public class ImportTest {

    @Autowired
    @Qualifier("client")
    private RestHighLevelClient restHighLevelClient;

    @Test
    void insert() {
　　　　　//csv文件2G，63W条数据，十多个字段
        String filePath = "D:\file\20211111.csv";

        LineIterator it = null;
        try {
            it = FileUtils.lineIterator(new File(filePath), "UTF-8");

        } catch (IOException e) {
            e.printStackTrace();
        }
        try {
            while (it.hasNext()) {
                String line = it.nextLine();
                //System.out.println("line = " + line);
                //文件是CSV文件，CSV文件中的每一列是用","隔开的，这样就可以得到每一列的元素
                String[] strArray = line.split(",");
                //有很长的空格，trim一下
                String name = strArray[6].trim();
                String code = strArray[8].trim();
                String num = strArray[11].trim();
                System.out.println(code + "==" + num);

                Entity entity = new Entity();
                entity.setCode(code);
                if (Objects.equals("xxx", code)) {
                    //跳过表头
                    continue;
                }
                entity.setNum(Long.parseLong(num));
                entity.setName(name);
                entity.setCreateTime(new Date());
                String index = "index20211111";
                singleInsert2(index, entity);
            }
        } finally {
            LineIterator.closeQuietly(it);
        }
    }

    @Test
    void batchInsert() {

        String filePath = "D:\express\20211111.csv";

        LineIterator it = null;
        try {
            it = FileUtils.lineIterator(new File(filePath), "UTF-8");

        } catch (IOException e) {
            e.printStackTrace();
        }
        try {
            int i = 0;
            List<Entity> entities = new ArrayList<>();

            while (it.hasNext()) {
                String line = it.nextLine();
                //System.out.println("line = " + line);
                String[] strArray = line.split(",");
                String code = strArray[6].trim();
                String name = strArray[8].trim();
                String num = strArray[11].trim();
                System.out.println(code + "==" + num);

                if (Objects.equals("xxx", code)) {
                    //跳过表头
                    continue;
                }
                Entity entity = new Entity();
                entity.setCode(code);
                entity.setName(name);
                try {
                    entity.setNum(Long.parseLong(num));
                } catch (NumberFormatException e) {
                    e.printStackTrace();
                    System.out.println("出错的数据" + code + "==" + num);
                }
                entity.setCreateTime(new Date());
                String index = "index20211111";

                //批量插入
                entities.add(entity);
                i++;
　　　　　　　　　　//如果最后一次批量插入不足10000条数据，需要再此根据实际条数特殊处理
                if (i % 10000 == 0) {
                    System.out.println("i = " + i);
                    try {
                        batchInsert2(index, entities);
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                    //清空已经处理过的list
                    entities.clear();
                    i = 0;
                }
            }
        } finally {
            LineIterator.closeQuietly(it);
        }
    }

    /**
     * 批量速度杠杠的
     *
     * @param index
     * @param entities
     * @throws IOException
     */
    public void batchInsert2(String index, List<Entity> entities) throws IOException {
        BulkRequest bulkRequest = new BulkRequest(index);
        System.out.println("entities.sz = " + entities.size());
        for (Entity org : entities) {
            IndexRequest request = new IndexRequest();
            request.source(JSON.toJSONString(org), XContentType.JSON);
            bulkRequest.add(request);
        }
        restHighLevelClient.bulk(bulkRequest, RequestOptions.DEFAULT);
    }

    /**
     * 数据量大，超级慢
     *
     * @param index
     * @param entity
     */
    public void singleInsert2(String index, Entity entity) {
        IndexRequest request = new IndexRequest(index);
        request.source(JSON.toJSONString(entity), XContentType.JSON);
        try {
            IndexResponse index1 = restHighLevelClient.index(request, RequestOptions.DEFAULT);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

实体类，需要什么字段自定义

package com.example.demo.entity;

import lombok.Data;

import java.util.Date;

/**
 * @author lhb
 * @date 2021/11/11
 * @since 1.0.0
 */
@Data
public class Entity {

    /**
     * 编码
     */
    private String code;
    /**
     * 名字
     */
    private String name;
    /**
     * 数量
     */
    private Long num;
    private Date createTime;

}

创建索引映射，然后插入数据：

PUT express_to_village20211104
{
  "settings": {
    "number_of_shards": 1,
    "number_of_replicas": 1
  },
  "mappings": {
    "properties": {
      "code": {
        "type": "keyword"
      },
      "name": {
        "type": "keyword"
      },
      "num": {
        "type": "long"
      },
      "createTime": {
        "type": "date"
      }
    }
  }
}

GET index20211111/_count
{}

#返回63w数据

{
“count” : 630000,
“_shards” : {
“total” : 1,
“successful” : 1,
“skipped” : 0,
“failed” : 0
}
}

GET index20211111/_search
{
  "query": {
    "constant_score": {
      "filter": {
        "terms": {
          "code": [
            2222,
            1111,
            3333
          ]
        }
      }
    }
  },
  "size": 1,
  "track_total_hits": true,
  "aggs": {
    "per_code": {
      "terms": {
        "field": "code",
        "size": 200
      },
      "aggs": {
        "num": {
          "sum": {
            "field": "num"
          }
        }
      }
    },
    "sum_num": {
      "sum": {
        "field": "num"
      }
    }
  }
}