当你去导出... - > Java - > JAR文件，点击下一步到达向导的第二页。在那里，您可以将此JAR的说明保存在工作区中。导出完成后，您应该有一个 .jardesc 文件。您可以右键单击此选项，然后选择创建JAR 以进行一步导出。

Do I have to always click to file/export/executable jar menu?
Is there any way to do this with one button?
(Because for example if I use netbeans and click the clean and build button it will also generate the jar file.)

When you go to Export... -> Java -> JAR File, click next to get to the second page of the wizard. There, you can Save the description of this JAR in the workspace. When the export completes, you should have a .jardesc file. You can right click on this and choose Create JAR for a one step export.