CSV文件的读取与数据类型转换的案例

 文件读取

文件内容范本在代码片段的最后注释段，分析可得出Customer 类。我们通过 commons.csv 工具包解析文件。从而获取到 List records 类型的数据。但CSVRecord的values 是 String[] 类型的 不符合我们的预期结果。

类型转换

• BeanWrapperImpl 为 bean 的属性赋值，当需要时做类型转换，走 Property

• DirectFieldAccessor 为 bean 的属性赋值，当需要时做类型转换，走 Field

 这里使用 BeanWrapperImpl，创建BeanWrapperImpl 并做转换前需要有两步操作，

1.设置要转换的对象（通过构造方法 BeanWrapperImpl(Object object)  ,或者setWrappedInstance(***) ）

2.添加 转换关系（requiredType -propertyEditor）查看源码

PropertyEditorRegistrySupport 字段以 Editors结尾的Map。如果没有设置转换关系则转换(convert***() )时候只会使用 defaultEditors 。此案例中对于Date 的字段类型无法满足，需要添加自定义的类型转换器(PropertyEditorSupport)-自定义时间转换器CustomDateEditor

import org.apache.commons.csv.CSVFormat;
import org.apache.commons.csv.CSVParser;
import org.apache.commons.csv.CSVRecord;
import org.junit.Test;
import org.springframework.beans.BeanWrapperImpl;
import org.springframework.beans.propertyeditors.CustomDateEditor;

import java.beans.IntrospectionException;
import java.io.FileReader;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.List;
import java.util.stream.Collectors;

/**
 * csv 文件读取与类型转换
 */
public class TestCSV {

    @Test
    public void main() throws IOException, IntrospectionException {
        // 目标文件
        FileReader fileReader = new FileReader("E:\\Users\\Desktop\\customer.txt");

        //示例标头与要读取文件的各个属性设置
        String str = "id|firstName|lastName|birthday";
        String[] heads = str.split("\\|"); // {"id", "firstName", "lastName", "birth"}
        CSVFormat csvFormat = CSVFormat.DEFAULT.builder()
                .setDelimiter('|')
                .setHeader(heads)
                .setSkipHeaderRecord(true)
                .build();

        // 解析文件并获取记录
        CSVParser parser = csvFormat.parse(fileReader);
        List records = parser.getRecords();

        // 设置类型转换器
        BeanWrapperImpl beanWrapper = new BeanWrapperImpl();
        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        beanWrapper.registerCustomEditor(Date.class, new CustomDateEditor(dateFormat, true));

        // 将String[] 转换为 Customer 类型的数据
        List customerList = records.stream().map(record -> {
            Customer newRecord = new Customer();
            beanWrapper.setWrappedInstance(newRecord);
            for (int i = 0; i < heads.length; i++) {
                beanWrapper.setPropertyValue(heads[i], record.get(i));
            }
            return newRecord;
        }).collect(Collectors.toList());
        System.out.println(customerList);
    }

}
//id|firstName|lastName|birthday
//1|Stone|Barrett|1964-10-19 14:11:03
//2|Raymond|Pace|1977-12-11 21:44:30
//3|Armando|Logan|1986-12-25 11:54:28
//4|Latifah|Barnett|1959-07-24 06:00:16
//5|Cassandra|Moses|1956-09-14 06:49:28
//6|Audra|Hopkins|1984-08-30 04:18:10
//7|Upton|Morrow|1973-82-04 05:26:05
//8|Melodie|Velasquez|1953-04-26 11:16:26
//9|Sybill|Nolan|1951-06-24 14:56:51
//10|Glenna|Little|1953-08-27 13:15:08
//11|Ingrid|Jackson|1957-09-05 21:36:47
//12|Duncan|Castaneda|1979-01-21 18:31:27
//13|Xaviera|Gillespie|1965-07-18 15:05:22
//14|Rhoda|Lancaster|1990-09-11 15:52:54
//15|Fatima|Combs|1979-06-01 06:58:54

@Data
public class Customer {
    private Integer id;

    private String firstName;

    private String lastName;

    private Date birth;

    pubilc Customer(){
    }
}