49.6. 3.DataField

DataField 注解定义字段的属性。每个 datafield 都由其在记录中的位置、类型（字符串、int、date、…​）以及可选的模式来标识

问题单 1：pos

这个参数/属性代表 csv 记录中字段的位置

position

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

    @DataField(pos = 1)
    private int orderNr;

    @DataField(pos = 5)
    private String isinCode;

}

如本例中所示，位置从 '1' 开始，但将继续在类 Order 中的 '5' 上。类客户端中定义了从 '2' 到 '4' 的数字（在此后参阅此）。

position 继续在另一个模型类中

public class Client {

    @DataField(pos = 2)
    private String clientNr;

    @DataField(pos = 3)
    private String firstName;

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

case 2 : pattern

该模式可以增强或验证您的数据格式

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;
}

case 3 : 精度

当您要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：位置在输出中有所不同

position 属性将告知如何将字段放在生成的 CSV 记录中。默认情况下，使用的位置与属性 'pos' 定义的位置对应。如果位置不同（这意味着我们有一个 asymetric 进程与来自 unmarshaling 分离）的比较，但我们可以使用"位置"来指示这一点。

下面是一个示例

位置在输出中有所不同

@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 的此属性必须与注释 @CsvRecord 的 attribute isOrdered = true 结合使用

case 5 : required

如果一个字段是必须的，只需使用 'required' setted to true

必填

@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，解析器会引发错误，其中包含以下信息：

缺少一些字段（可选或强制），行 :

case 6 : trim

如果某个字段在处理前带有前应删除的前导和/或尾随空格，只需使用属性 'trim' setted 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

如果没有定义字段，则使用 defaultValue 属性所示的值

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。