Write java bean to Csv Table format

Question

Is there any way to write Java bean to Csv table format using Open Csv ? What are the other libraries available to achieve this ?

Answer 1

uniVocity-parsers support for conversions to and from java beans is unmatched. Here's a simple example of a class:

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;
}

Now, to write instances to a file, do this:

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

The library offers many configuration options and ways to achieve what you want. If you find yourself using the same annotations over and over again, just define a meta-annotation. For example, apply a replacement conversion over fields that contain the ` character, instead of declaring this in every single field:

@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;

You can create a meta-annotatin like this:

@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;

And use it in your class like this:

@MyReplacement
public String fieldA;

@MyReplacement(field = "BB")
public String fieldB;

@MyReplacement(myIndex = 4)
public String fieldC;
}

I hope it helps.

Disclaimer: I'm the author of this library, it's open-source and free (Apache V2.0 license)