jasperreport生成pdf_jasperreport 导出excel_jasperreport json(49)

height will not be adapted, because it will ruin the already created layout.

Suppressing Null Values Display

If the text field expression returns null, your text field will display the "null" text in the generated

document. A way to avoid this is to set the isBlankWhenNull attribute to "true". By doing

this, the text field will cease to display "null" and will display an empty string. This way nothing will

appear on your document if the text field value is null.

Formatting Output

Of course, when dealing with numeric or date/time values, you could use the Java API to format the

output of the text field expressions yourself. But there is a more convenient way to do it: by using the

pattern attribute available in the <textField> element.

The value you should supply to this attribute is the same that you would supply if it were for you to

format the value using either the java.text.DecimalFormat class or

java.text.SimpleDateFormat class, depending on the type of value to format.

In fact, what the engine does is to instantiate the java.text.DecimalFormat class if the text field

expression returns subclasses of the java.lang.Number class or to instantiate the

java.text.SimpleDataFormat if the text field expression return java.util.Date or

java.sql.Timestamp objects.

For more detail about the syntax of this pattern attribute, check the Java API documentation for those

two classes: java.text.DecimalFormat and java.text.SimpleDateFormat.

The JasperReports Ultimate Guide

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