带列标题的StatefulBeanToCsv

• Z时代
• 2024-01-10
• 分类：问答

我正在opencsv-4.0编写一个csv文件，我需要在输出文件中添加列标题。

这是我的代码。

public static void buildProductCsv(final List<Product> product,
        final String filePath) {
    try {
        Writer writer = new FileWriter(filePath);
        // mapping of columns with their positions
        ColumnPositionMappingStrategy<Product> mappingStrategy = new ColumnPositionMappingStrategy<Product>();
        // Set mappingStrategy type to Product Type
        mappingStrategy.setType(Product.class);
        // Fields in Product Bean
        String[] columns = new String[] { "productCode", "MFD", "EXD" };
        // Setting the colums for mappingStrategy
        mappingStrategy.setColumnMapping(columns);
        StatefulBeanToCsvBuilder<Product> builder = new StatefulBeanToCsvBuilder<Product>(writer);
        StatefulBeanToCsv<Product> beanWriter = builder.withMappingStrategy(mappingStrategy).build();
        // Writing data to csv file
        beanWriter.write(product);
        writer.close();
        log.info("Your csv file has been generated!");
    } catch (Exception ex) {
        log.warning("Exception: " + ex.getMessage());
    }
}

上面的代码用数据创建一个csv文件。但该文件中不包括列标题。

如何添加列标题以输出csv？

回答：

ColumnPositionMappingStrategy＃generateHeader返回空数组

/**
 * This method returns an empty array.
 * The column position mapping strategy assumes that there is no header, and
 * thus it also does not write one, accordingly.
 * @return An empty array
 */
@Override
public String[] generateHeader() {
    return new String[0];
}

如果从BeanToCsv构建器中删除MappingStrategy

// replace 
StatefulBeanToCsv<Product> beanWriter = builder.withMappingStrategy(mappingStrategy).build();
// with
StatefulBeanToCsv<Product> beanWriter = builder.build();

它将产品的类成员写为CSV标头

如果您的产品类成员名称是

"productCode", "MFD", "EXD"

这应该是正确的解决方案

否则，添加@CsvBindByName批注

import com.opencsv.bean.CsvBindByName;
import com.opencsv.bean.StatefulBeanToCsv;
import com.opencsv.bean.StatefulBeanToCsvBuilder;
import java.io.FileWriter;
import java.io.Writer;
import java.util.ArrayList;
import java.util.List;
public class CsvTest {
    public static void main(String[] args) throws Exception {
        Writer writer = new FileWriter(fileName);
        StatefulBeanToCsvBuilder<Product> builder = new StatefulBeanToCsvBuilder<>(writer);
        StatefulBeanToCsv<Product> beanWriter = builder.build();
        List<Product> products = new ArrayList<>();
        products.add(new Product("1", "11", "111"));
        products.add(new Product("2", "22", "222"));
        products.add(new Product("3", "33", "333"));
        beanWriter.write(products);
        writer.close();
    }
    public static class Product {
        @CsvBindByName(column = "productCode")
        String id;
        @CsvBindByName(column = "MFD")
        String member2;
        @CsvBindByName(column = "EXD")
        String member3;
        Product(String id, String member2, String member3) {
            this.id = id;
            this.member2 = member2;
            this.member3 = member3;
        }
        public String getId() {
            return id;
        }
        public void setId(String id) {
            this.id = id;
        }
        public String getMember2() {
            return member2;
        }
        public void setMember2(String member2) {
            this.member2 = member2;
        }
        public String getMember3() {
            return member3;
        }
        public void setMember3(String member3) {
            this.member3 = member3;
        }
    }
}

输出：

“ EXD”，“ MFD”，“ PRODUCTCODE”

“ 111”，“ 11”，“ 1”

“ 222”，“ 22”，“ 2”

“ 333”，“ 33”，“ 3”

请注意; 班级，由于OpenCSV库使用了Reflection，所以getter和setter程序需要公开

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