jasperreport生成pdf_jasperreport 导出excel_jasperreport json(56)

chose only later in the report filling process, due to complex algorithms or whatever.

The same attributes, evaluationTime and evaluationGroup, that we have talked about in the text

fields section are available also in the <image> element. The evaluationTime attribute can have the

following values:

_ Immediate evaluation: The image expression is evaluated when filling the current band

(evaluationTime="Now").

_ End of report evaluation: The image expression is evaluated when reaching the end of the report

(evaluationTime="Report").

_ End of page evaluation: The image expression is evaluated when reaching the end of the current

page (evaluationTime="Page").

The JasperReports Ultimate Guide

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_ End of column evaluation: The image expression is evaluated when reaching the end of the current

column (evaluationTime="Column").

_ End of group evaluation: The image expression is evaluated when the group specified by the

evaluationGroup attribute changes (evaluationTime="Group").

The default value for this attribute is "Now".

Image Expression

The value returned by the image expression is used as the source for the image that is going to be

displayed. The image expression is introduced by the <imageExpression> element and can return

values from only a limited range of classes listed below:

java.lang.String

java.io.File

java.net.URL

java.io.InputStream

java.awt.Image

When the image expression returns a java.lang.String value, the engine will try to see

whether the value represents an URL from which to load the image. If it is not a valid URL

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