There are several ways in which this library will allow you to create Excel files.
The generic way is:
// Get the factory Java2ExcelDtdFactory factory = Java2ExcelDtdFactory.getInstance(); // Use the factory to get the instance to the configurer Java2ExcelDtd java2ExcelDtd = factory. [...]; // Construct the ExcelWritter ExcelWritter excelWritter = new ExcelWritter(); // Get your collection ready Collection col = [...]; // Add the collection to the excel // You can add as many of these as you want. Each one // will go to a different excel Sheet. excelWritter.addReport(col, java2ExcelDtd); // Finally, save the excel to a File or OutputStream excelWritter.saveTo(new File("someExcel.xls"))
The major differences show up at the time of getting an instance of a Java2ExcelDtd.
Using an xml file gives you the most flexible way of making you excel file, allowing you to configure things such as column titles. You have an xml example here.
// Get your xml file as input stream InputStream yourXmlInputStream = [...]; // Parse it and make the config object Java2ExcelDtd java2ExcelDtd = factory.readFromFile(yourXmlInputStream);
You can get a Java2ExcelDtd without needing to configure any xml file. This way, every property has to be read by reflection.
// Define until which level the properties should be read int includeExtraLevel = 1; Java2ExcelDtd java2ExcelDtd = factory.defaultJava2ExcelDtd(includeExtraLevel);
includeExtraLevel parameter is very important
because it defines until which level the properties will be looked
Posible values are:
defaultJava2ExcelDtd() method is overloaded. There
are two more versions that allow you to set different java types to
ignore while scanning recursively for properties.
The final aproach is to use an xml file that allows you to also scan properties by reflection.
You use the xml file as explained
before, but in the xml
file you set the parameter
includeExtraLevel to the
properties tag with a value greater than or equals to
In the java code, you must note that the
readFromFile() method from the Java2ExcelDtdFactory
is overloaded. There are two more versions that allow you to set
different java types to ignore while scanning recursively for
The following is an example xml file that I use in one of the tests. It is commented pretty well enough, I think.
<?xml version="1.0" encoding="ISO-8859-1"?> <!DOCTYPE java2excel PUBLIC "-//epere4/DTD Java2Excel mapping file//EN" "http://java2excel.sourceforge.net/dtd/java2excel-mapping.dtd"> <java2excel> <!-- This header is here just for future enhancements. Don't use it. You can even ommit the header if you want. Please note that future versions may not support any CDATA inside the header tags. --> <header> nothing for now </header> <body> <!-- Setting an includeExtraLevel="1" makes the excel writer to scan (by reflection) all the properties in levels 1 and 0 of each element in the collection. The default value here is includeExtraLevel = "-1" which means no reflection scan at all. --> <properties includeExtraLevel="1"> <!-- expression is an ognl expression that will be applied to each element in the collection to obtain its value. In the road to getting the value some problems may arrise, such as a property being inexistent or null. With protectNullPointer="true" (which is the default value, by the way) all exception of this kind will be ignored and an empty cell will go to excel. --> <property expression="text" protectNullPointer="true"> <description> This is a text property. </description> </property> <property expression="integerNumber" protectNullPointer="false"/> <property expression="date"/> <property expression="calendar"/> <property expression="boolValue"/> <!-- If the title parameter is set, then the excel column will have that text as title. If parameter is ommited, then the column name will be exactly what you put in expression. --> <property expression="internal.integerNumber" title="Interal Integer Number"/> <property expression="internal.date" title="ESTE ES NULL"/> <property expression="internal2.integerNumber" protectNullPointer="true"/> </properties> </body> </java2excel>
expression attributes are
ognl expressions that are
applied to each element in the collection.
integerNumber will be traduced to something like
elementInCollection being the name of the variable for
each element in the collection, of course).
A more complex expresion like
internal.integerNumber is equivalent to
. An exception could be thrown here if
null, for example. These kind of situations can be
avoided with the parameter