48.5. 3.DataField

DataField 注释定义字段的属性。每个数据字段都由其在记录中的位置、类型（字符串、int、date、…​）以及可选的模式识别

case 1 : pos

此参数/attribute 代表 csv 记录中字段的位置

位置

@CsvRecord(separator = ",")
public class Order {

    @DataField(pos = 1)
    private int orderNr;

    @DataField(pos = 5)
    private String isinCode;

}

如您在本例中看到的那样，位置从 '1' 开始，但在类 Order 中继续为 '5'。从 '2' 到 '4' 的数字在类客户端中定义（请参见下文之后）。

在另一个模型类中继续位置

public class Client {

    @DataField(pos = 2)
    private String clientNr;

    @DataField(pos = 3)
    private String firstName;

    @DataField(pos = 4)
    private String lastName;
}

case 2 : pattern

模式允许增强或验证数据格式

pattern

@CsvRecord(separator = ",")
public class Order {

    @DataField(pos = 1)
    private int orderNr;

    @DataField(pos = 5)
    private String isinCode;

    @DataField(name = "Name", pos = 6)
    private String instrumentName;

    @DataField(pos = 7, precision = 2)
    private BigDecimal amount;

    @DataField(pos = 8)
    private String currency;

    // pattern used during parsing or when the date is created
    @DataField(pos = 9, pattern = "dd-MM-yyyy")
    private Date orderDate;
}

案例 3：精准

当您想定义数字的十进制部分时，精度非常有用

精度

@CsvRecord(separator = ",")
public class Order {

    @DataField(pos = 1)
    private int orderNr;

    @Link
    private Client client;

    @DataField(pos = 5)
    private String isinCode;

    @DataField(name = "Name", pos = 6)
    private String instrumentName;

    @DataField(pos = 7, precision = 2)
    private BigDecimal amount;

    @DataField(pos = 8)
    private String currency;

    @DataField(pos = 9, pattern = "dd-MM-yyyy")
    private Date orderDate;
}

问题单 4：输出中的 Position 不同

position 属性将告知绑定如何在生成的 CSV 记录中放置字段。默认情况下，使用的位置与通过属性 'pos' 定义的位置对应。如果位置不同（即，我们有一种可以比可以使用"组成"比较出的统计处理过程对比）来说明这一点。

下面是一个示例

输出中位置不同

@CsvRecord(separator = ",", isOrdered = true)
public class Order {

    // Positions of the fields start from 1 and not from 0

    @DataField(pos = 1, position = 11)
    private int orderNr;

    @DataField(pos = 2, position = 10)
    private String clientNr;

    @DataField(pos = 3, position = 9)
    private String firstName;

    @DataField(pos = 4, position = 8)
    private String lastName;

    @DataField(pos = 5, position = 7)
    private String instrumentCode;

    @DataField(pos = 6, position = 6)
    private String instrumentNumber;
}

注释 @DataField 的此属性必须与属性 isOrdered = true 结合使用。

问题单 5：必需

如果字段是必须的，只需使用将属性 'required' 设为 true

必需

@CsvRecord(separator = ",")
public class Order {

    @DataField(pos = 1)
    private int orderNr;

    @DataField(pos = 2, required = true)
    private String clientNr;

    @DataField(pos = 3, required = true)
    private String firstName;

    @DataField(pos = 4, required = true)
    private String lastName;
}

如果记录中没有此字段，解析器会使用以下信息来引发错误：

有些字段缺失（可选或强制），行：

case 6 : trim

如果字段具有前应该删除的前导和/或尾随空格，只需将属性 'trim' 设置为 true

Trim

@CsvRecord(separator = ",")
public class Order {

    @DataField(pos = 1, trim = true)
    private int orderNr;

    @DataField(pos = 2, trim = true)
    private Integer clientNr;

    @DataField(pos = 3, required = true)
    private String firstName;

    @DataField(pos = 4)
    private String lastName;
}

case 7 : defaultValue

如果未定义字段，则使用 defaultValue 属性指示的值

默认值

@CsvRecord(separator = ",")
public class Order {

    @DataField(pos = 1)
    private int orderNr;

    @DataField(pos = 2)
    private Integer clientNr;

    @DataField(pos = 3, required = true)
    private String firstName;

    @DataField(pos = 4, defaultValue = "Barin")
    private String lastName;
}

此属性仅适用于可选字段。