iReport 子报表 Error loading object from URL

今天，制作iReport子报表出现一个头疼的问题，与之前子报表做法几乎一样，jasper文件路径也正确，通过浏览器可以下载；

但是偏偏SUBREPORT_DIR设置为"F:\\iReport-3.0.0\\"可以运行，而设置"http://localhost:8080/"类似路径却始终不行，为何呢？

net.sf.jasperreports.engine.JRException: Error loading object from URL : http://localhost:8080//xxx_subreport0.jasper at net.sf.jasperreports.engine.util.JRLoader.loadObject(JRLoader.java:149)
at net.sf.jasperreports.engine.util.JRLoader.loadObjectFromLocation(JRLoader.java:256)
at net.sf.jasperreports.engine.fill.JRFillSubreport.evaluateSubreport(JRFillSubreport.java:311)
at net.sf.jasperreports.engine.fill.JRFillSubreport.evaluate(JRFillSubreport.java:260)
at net.sf.jasperreports.engine.fill.JRFillElementContainer.evaluate(JRFillElementContainer.java:275)
at net.sf.jasperreports.engine.fill.JRFillBand.evaluate(JRFillBand.java:426)
at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillColumnBand(JRVerticalFiller.java:1380)
at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillDetail(JRVerticalFiller.java:692)
at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReportStart(JRVerticalFiller.java:255)
at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReport(JRVerticalFiller.java:113)
at net.sf.jasperreports.engine.fill.JRBaseFiller.fill(JRBaseFiller.java:888)
at net.sf.jasperreports.engine.fill.JRBaseFiller.fill(JRBaseFiller.java:791)
at net.sf.jasperreports.engine.fill.JRFiller.fillReport(JRFiller.java:63)
at net.sf.jasperreports.engine.JasperFillManager.fillReport(JasperFillManager.java:402)
Caused by: java.io.IOException: Server returned HTTP response code: 505 for URL: http://localhost:8080//xxx_subreport0.jasper at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1441)
at java.net.URL.openStream(URL.java:1010)
at net.sf.jasperreports.engine.util.JRLoader.loadObject(JRLoader.java:143)
... 86 more

最后，经过个各种尝试，终于找到了原因，解决方案：我的子报表中有空格，编译出的jasper文件也是，浏览器中读不出来，空格改成下划线即可。

（附：jasperreports-3.0.0相关API：http://www.docjar.com/projects/jasperreports-3.0.0-project-code.html）