将 java bean 写入 csv 表格式

Question

有没有办法使用Open Csv将Java Bean写入Csv表格式？还有哪些其他库可用于实现此目的？

Answer 1

uniVocity-parsers对Java Bean之间的转换的支持是无与伦比的。下面是一个类的简单示例：

public class TestBean {
    // if the value parsed in the quantity column is "?" or "-", it will be replaced by null.
    @NullString(nulls = {"?", "-"})
    // if a value resolves to null, it will be converted to the String "0".
    @Parsed(defaultNullRead = "0")
    private Integer quantity
    @Trim
    @LowerCase
    @Parsed(index = 4)
    private String comments;
    // you can also explicitly give the name of a column in the file.
    @Parsed(field = "amount")
    private BigDecimal value;
    @Trim
    @LowerCase
    // values "no", "n" and "null" will be converted to false; values "yes" and "y" will be converted to true
    @BooleanString(falseStrings = {"no", "n", "null"}, trueStrings = {"yes", "y"})
    @Parsed
    private Boolean pending;
}

现在，要将实例写入文件，请执行以下操作：

Collection<TestBean> beansToWrite = someMethodThatProducesTheObjectYouWant();
File output = new File("/path/to/output.csv");
new CsvRoutines().writeAll(beansToWrite, TestBean.class, output, Charset.forName("UTF-8"));

该库提供了许多配置选项和实现所需内容的方法。如果您发现自己一遍又一遍地使用相同的注释，只需定义一个元注释即可。例如，对包含 ' 字符的字段应用替换转换，而不是在每个字段中声明：

@Parsed
@Replace(expression = "`", replacement = "")
public String fieldA;
@Parsed(field = "BB")
@Replace(expression = "`", replacement = "")
public String fieldB;
@Parsed(index = 4)
@Replace(expression = "`", replacement = "")
public String fieldC;

您可以像这样创建一个元注释：

@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Target({ElementType.FIELD, ElementType.METHOD, ElementType.ANNOTATION_TYPE})
@Replace(expression = "`", replacement = "")
@Parsed
public @interface MyReplacement {
@Copy(to = Parsed.class)
String field() default "";
@Copy(to = Parsed.class, property = "index")
int myIndex() default -1;

并在您的课堂中像这样使用它：

@MyReplacement
public String fieldA;
@MyReplacement(field = "BB")
public String fieldB;
@MyReplacement(myIndex = 4)
public String fieldC;
}

我希望它有所帮助。

免责声明：我是这个库的作者，它是开源的，免费的（Apache V2.0许可证）