Violet crashes when loading large diagrams
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#30 Violet crashes when loading large diagrams
I'm teaching a software engineering course at the University of Washington. Our students make rather large class/sequence diagrams. Many of the groups' diagrams don't open up in Violet for us. This is on any platform. The error still occurs if I run Violet with the -Xmx1024m -Xms1024m flags to give it more memory. I've attached one of the offending diagrams.
The worst thing about this error is that in the latest violet, it now permanently breaks Violet because Violet tries to put the diagram in the recent files list, and that crashes as well.
Below is a partial trace of the exception output we see when we run Violet on these diagrams.
-- Marty Stepp
java.lang.ClassNotFoundException: com.horstmann.violet.framework.PointNode
at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:276)
at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:247)
at com.sun.beans.ObjectHandler.classForName(ObjectHandler.java:68)
at com.sun.beans.ObjectHandler.classForName(ObjectHandler.java:55)
at com.sun.beans.ObjectHandler.classForName2(ObjectHandler.java:159)
at com.sun.beans.ObjectHandler.startElement(ObjectHandler.java:194)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.startElement(AbstractSAXPars
er.java:453)
at com.sun.org.apache.xerces.internal.parsers.AbstractXMLDocumentParser.emptyElement(Abstrac
tXMLDocumentParser.java:179)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanStartElement(X
MLDocumentFragmentScannerImpl.java:1337)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDri
ver.next(XMLDocumentFragmentScannerImpl.java:2740)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImp
l.java:645)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDo
cumentFragmentScannerImpl.java:508)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.ja
va:807)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.ja
va:737)
at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:107)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java
:1205)
at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.j
ava:522)
at javax.xml.parsers.SAXParser.parse(SAXParser.java:364)
at javax.xml.parsers.SAXParser.parse(SAXParser.java:142)
at java.beans.XMLDecoder.getHandler(XMLDecoder.java:238)
at java.beans.XMLDecoder.readObject(XMLDecoder.java:201)
at com.horstmann.violet.framework.diagram.GraphService.readGraph(GraphService.java:280)
at com.horstmann.violet.framework.action.FileAction.open(FileAction.java:150)
at com.horstmann.violet.framework.action.FileAction.open(FileAction.java:175)
at com.horstmann.violet.UMLEditor.createWorkspace(UMLEditor.java:195)
at com.horstmann.violet.UMLEditor.main(UMLEditor.java:102)
java.lang.NullPointerException: target should not be null
at java.beans.Statement.invoke(Statement.java:131)
at java.beans.Expression.getValue(Expression.java:98)
at com.sun.beans.MutableExpression.getValue(ObjectHandler.java:445)
at com.sun.beans.ObjectHandler.getValue(ObjectHandler.java:108)
at com.sun.beans.ObjectHandler.endElement(ObjectHandler.java:372)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.endElement(AbstractSAXParser
.java:593)
at com.sun.org.apache.xerces.internal.parsers.AbstractXMLDocumentParser.emptyElement(Abstrac
tXMLDocumentParser.java:180)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanStartElement(X
MLDocumentFragmentScannerImpl.java:1337)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDri
ver.next(XMLDocumentFragmentScannerImpl.java:2740)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImp
l.java:645)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDo
cumentFragmentScannerImpl.java:508)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.ja
va:807)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.ja
va:737)
at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:107)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java
:1205)
at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.j
ava:522)
at javax.xml.parsers.SAXParser.parse(SAXParser.java:364)
at javax.xml.parsers.SAXParser.parse(SAXParser.java:142)
at java.beans.XMLDecoder.getHandler(XMLDecoder.java:238)
at java.beans.XMLDecoder.readObject(XMLDecoder.java:201)
at com.horstmann.violet.framework.diagram.GraphService.readGraph(GraphService.java:280)
at com.horstmann.violet.framework.action.FileAction.open(FileAction.java:150)
at com.horstmann.violet.framework.action.FileAction.open(FileAction.java:175)
at com.horstmann.violet.UMLEditor.createWorkspace(UMLEditor.java:195)
at com.horstmann.violet.UMLEditor.main(UMLEditor.java:102)
java.lang.NullPointerException
at com.horstmann.violet.framework.diagram.Graph.addNode(Graph.java:420)
at sun.reflect.GeneratedMethodAccessor8.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:36)
at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:243)
at java.beans.Statement.invoke(Statement.java:214)
at java.beans.Expression.getValue(Expression.java:98)
at com.sun.beans.MutableExpression.getValue(ObjectHandler.java:445)
at com.sun.beans.ObjectHandler.getValue(ObjectHandler.java:108)
at com.sun.beans.ObjectHandler.endElement(ObjectHandler.java:372)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.endElement(AbstractSAXParser
.java:593)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanEndElement(XML
DocumentFragmentScannerImpl.java:1772)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDri
ver.next(XMLDocumentFragmentScannerImpl.java:2923)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImp
l.java:645)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDo
cumentFragmentScannerImpl.java:508)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.ja
va:807)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.ja
va:737)
at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:107)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java
:1205)
at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.j
ava:522)
at javax.xml.parsers.SAXParser.parse(SAXParser.java:364)
at javax.xml.parsers.SAXParser.parse(SAXParser.java:142)
at java.beans.XMLDecoder.getHandler(XMLDecoder.java:238)
at java.beans.XMLDecoder.readObject(XMLDecoder.java:201)
at com.horstmann.violet.framework.diagram.GraphService.readGraph(GraphService.java:280)
at com.horstmann.violet.framework.action.FileAction.open(FileAction.java:150)
at com.horstmann.violet.framework.action.FileAction.open(FileAction.java:175)
at com.horstmann.violet.UMLEditor.createWorkspace(UMLEditor.java:195)
at com.horstmann.violet.UMLEditor.main(UMLEditor.java:102)
java.lang.ClassNotFoundException: com.horstmann.violet.framework.PointNode
at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:276)
at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:247)
at com.sun.beans.ObjectHandler.classForName(ObjectHandler.java:68)
at com.sun.beans.ObjectHandler.classForName(ObjectHandler.java:55)
at com.sun.beans.ObjectHandler.classForName2(ObjectHandler.java:159)
at com.sun.beans.ObjectHandler.startElement(ObjectHandler.java:194)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.startElement(AbstractSAXPars
er.java:453)
at com.sun.org.apache.xerces.internal.parsers.AbstractXMLDocumentParser.emptyElement(Abstrac
tXMLDocumentParser.java:179)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanStartElement(X
MLDocumentFragmentScannerImpl.java:1337)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDri
ver.next(XMLDocumentFragmentScannerImpl.java:2740)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImp
l.java:645)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDo
cumentFragmentScannerImpl.java:508)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.ja
va:807)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.ja
va:737)
at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:107)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java
:1205)
at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.j
ava:522)
at javax.xml.parsers.SAXParser.parse(SAXParser.java:364)
at javax.xml.parsers.SAXParser.parse(SAXParser.java:142)
at java.beans.XMLDecoder.getHandler(XMLDecoder.java:238)
at java.beans.XMLDecoder.readObject(XMLDecoder.java:201)
at com.horstmann.violet.framework.diagram.GraphService.readGraph(GraphService.java:280)
at com.horstmann.violet.framework.action.FileAction.open(FileAction.java:150)
at com.horstmann.violet.framework.action.FileAction.open(FileAction.java:175)
at com.horstmann.violet.UMLEditor.createWorkspace(UMLEditor.java:195)
at com.horstmann.violet.UMLEditor.main(UMLEditor.java:102)
java.lang.NullPointerException: target should not be null
at java.beans.Statement.invoke(Statement.java:131)
at java.beans.Expression.getValue(Expression.java:98)
at com.sun.beans.MutableExpression.getValue(ObjectHandler.java:445)
at com.sun.beans.ObjectHandler.getValue(ObjectHandler.java:108)
at com.sun.beans.ObjectHandler.endElement(ObjectHandler.java:372)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.endElement(AbstractSAXParser
.java:593)
at com.sun.org.apache.xerces.internal.parsers.AbstractXMLDocumentParser.emptyElement(Abstrac
tXMLDocumentParser.java:180)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanStartElement(X
MLDocumentFragmentScannerImpl.java:1337)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDri
ver.next(XMLDocumentFragmentScannerImpl.java:2740)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImp
l.java:645)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDo
cumentFragmentScannerImpl.java:508)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.ja
va:807)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.ja
va:737)
at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:107)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java
:1205)
at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.j
ava:522)
at javax.xml.parsers.SAXParser.parse(SAXParser.java:364)
at javax.xml.parsers.SAXParser.parse(SAXParser.java:142)
at java.beans.XMLDecoder.getHandler(XMLDecoder.java:238)
at java.beans.XMLDecoder.readObject(XMLDecoder.java:201)
at com.horstmann.violet.framework.diagram.GraphService.readGraph(GraphService.java:280)
at com.horstmann.violet.framework.action.FileAction.open(FileAction.java:150)
at com.horstmann.violet.framework.action.FileAction.open(FileAction.java:175)
at com.horstmann.violet.UMLEditor.createWorkspace(UMLEditor.java:195)
at com.horstmann.violet.UMLEditor.main(UMLEditor.java:102)
java.lang.NullPointerException
at com.horstmann.violet.framework.diagram.Graph.addNode(Graph.java:420)
at sun.reflect.GeneratedMethodAccessor8.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:36)
at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:243)
at java.beans.Statement.invoke(Statement.java:214)
at java.beans.Expression.getValue(Expression.java:98)
at com.sun.beans.MutableExpression.getValue(ObjectHandler.java:445)
at com.sun.beans.ObjectHandler.getValue(ObjectHandler.java:108)
at com.sun.beans.ObjectHandler.endElement(ObjectHandler.java:372)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.endElement(AbstractSAXParser
.java:593)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanEndElement(XML
DocumentFragmentScannerImpl.java:1772)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDri
ver.next(XMLDocumentFragmentScannerImpl.java:2923)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImp
l.java:645)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDo
cumentFragmentScannerImpl.java:508)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.ja
va:807)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.ja
va:737)
at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:107)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java
:1205)
at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.j
ava:522)
at javax.xml.parsers.SAXParser.parse(SAXParser.java:364)
at javax.xml.parsers.SAXParser.parse(SAXParser.java:142)
at java.beans.XMLDecoder.getHandler(XMLDecoder.java:238)
at java.beans.XMLDecoder.readObject(XMLDecoder.java:201)
at com.horstmann.violet.framework.diagram.GraphService.readGraph(GraphService.java:280)
at com.horstmann.violet.framework.action.FileAction.open(FileAction.java:150)
at com.horstmann.violet.framework.action.FileAction.open(FileAction.java:175)
at com.horstmann.violet.UMLEditor.createWorkspace(UMLEditor.java:195)
at com.horstmann.violet.UMLEditor.main(UMLEditor.java:102)
java.lang.ClassNotFoundException: com.horstmann.violet.framework.PointNode
at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:276)
at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:247)
at com.sun.beans.ObjectHandler.classForName(ObjectHandler.java:68)
at com.sun.beans.ObjectHandler.classForName(ObjectHandler.java:55)
at com.sun.beans.ObjectHandler.classForName2(ObjectHandler.java:159)
at com.sun.beans.ObjectHandler.startElement(ObjectHandler.java:194)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.startElement(AbstractSAXPars
er.java:453)
at com.sun.org.apache.xerces.internal.parsers.AbstractXMLDocumentParser.emptyElement(Abstrac
tXMLDocumentParser.java:179)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanStartElement(X
MLDocumentFragmentScannerImpl.java:1337)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDri
ver.next(XMLDocumentFragmentScannerImpl.java:2740)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImp
l.java:645)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDo
cumentFragmentScannerImpl.java:508)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.ja
va:807)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.ja
va:737)
at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:107)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java
:1205)
at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.j
ava:522)
at javax.xml.parsers.SAXParser.parse(SAXParser.java:364)
at javax.xml.parsers.SAXParser.parse(SAXParser.java:142)
at java.beans.XMLDecoder.getHandler(XMLDecoder.java:238)
at java.beans.XMLDecoder.readObject(XMLDecoder.java:201)
at com.horstmann.violet.framework.diagram.GraphService.readGraph(GraphService.java:280)
at com.horstmann.violet.framework.action.FileAction.open(FileAction.java:150)
at com.horstmann.violet.framework.action.FileAction.open(FileAction.java:175)
at com.horstmann.violet.UMLEditor.createWorkspace(UMLEditor.java:195)
at com.horstmann.violet.UMLEditor.main(UMLEditor.java:102)
java.lang.NullPointerException: target should not be null
at java.beans.Statement.invoke(Statement.java:131)
at java.beans.Expression.getValue(Expression.java:98)
at com.sun.beans.MutableExpression.getValue(ObjectHandler.java:445)
at com.sun.beans.ObjectHandler.getValue(ObjectHandler.java:108)
at com.sun.beans.ObjectHandler.endElement(ObjectHandler.java:372)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.endElement(AbstractSAXParser
.java:593)
at com.sun.org.apache.xerces.internal.parsers.AbstractXMLDocumentParser.emptyElement(Abstrac
tXMLDocumentParser.java:180)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanStartElement(X
MLDocumentFragmentScannerImpl.java:1337)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDri
ver.next(XMLDocumentFragmentScannerImpl.java:2740)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImp
l.java:645)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDo
cumentFragmentScannerImpl.java:508)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.ja
va:807)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.ja
va:737)
at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:107)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java
:1205)
at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.j
ava:522)
at javax.xml.parsers.SAXParser.parse(SAXParser.java:364)
at javax.xml.parsers.SAXParser.parse(SAXParser.java:142)
at java.beans.XMLDecoder.getHandler(XMLDecoder.java:238)
at java.beans.XMLDecoder.readObject(XMLDecoder.java:201)
at com.horstmann.violet.framework.diagram.GraphService.readGraph(GraphService.java:280)
at com.horstmann.violet.framework.action.FileAction.open(FileAction.java:150)
at com.horstmann.violet.framework.action.FileAction.open(FileAction.java:175)
at com.horstmann.violet.UMLEditor.createWorkspace(UMLEditor.java:195)
at com.horstmann.violet.UMLEditor.main(UMLEditor.java:102)
java.lang.NullPointerException
at com.horstmann.violet.framework.diagram.Graph.addNode(Graph.java:420)
at sun.reflect.GeneratedMethodAccessor8.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:36)
at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:243)
at java.beans.Statement.invoke(Statement.java:214)
at java.beans.Expression.getValue(Expression.java:98)
at com.sun.beans.MutableExpression.getValue(ObjectHandler.java:445)
at com.sun.beans.ObjectHandler.getValue(ObjectHandler.java:108)
at com.sun.beans.ObjectHandler.endElement(ObjectHandler.java:372)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.endElement(AbstractSAXParser
.java:593)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanEndElement(XML
DocumentFragmentScannerImpl.java:1772)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDri
ver.next(XMLDocumentFragmentScannerImpl.java:2923)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImp
l.java:645)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDo
cumentFragmentScannerImpl.java:508)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.ja
va:807)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.ja
va:737)
at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:107)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java
:1205)
at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.j
ava:522)
at javax.xml.parsers.SAXParser.parse(SAXParser.java:364)
at javax.xml.parsers.SAXParser.parse(SAXParser.java:142)
at java.beans.XMLDecoder.getHandler(XMLDecoder.java:238)
at java.beans.XMLDecoder.readObject(XMLDecoder.java:201)
at com.horstmann.violet.framework.diagram.GraphService.readGraph(GraphService.java:280)
at com.horstmann.violet.framework.action.FileAction.open(FileAction.java:150)
at com.horstmann.violet.framework.action.FileAction.open(FileAction.java:175)
at com.horstmann.violet.UMLEditor.createWorkspace(UMLEditor.java:195)
at com.horstmann.violet.UMLEditor.main(UMLEditor.java:102)
java.lang.NullPointerException: target should not be null
at java.beans.Statement.invoke(Statement.java:131)
at java.beans.Expression.getValue(Expression.java:98)
at com.sun.beans.MutableExpression.getValue(ObjectHandler.java:445)
at com.sun.beans.ObjectHandler.getValue(ObjectHandler.java:108)
at com.sun.beans.ObjectHandler.lookup(ObjectHandler.java:346)
at com.sun.beans.ObjectHandler.startElement(ObjectHandler.java:275)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.startElement(AbstractSAXPars
er.java:453)
at com.sun.org.apache.xerces.internal.parsers.AbstractXMLDocumentParser.emptyElement(Abstrac
tXMLDocumentParser.java:179)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanStartElement(X
MLDocumentFragmentScannerImpl.java:1337)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDri
ver.next(XMLDocumentFragmentScannerImpl.java:2740)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImp
l.java:645)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDo
cumentFragmentScannerImpl.java:508)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.ja
va:807)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.ja
va:737)
at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:107)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java
class diagram that causes the error