Use Case

When a runtime error happens in data binding, it's hard to know which page, which component, which expression that causes it.

org.zkoss.zel.PropertyNotFoundException: Target Unreachable, '4' returned null
at org.zkoss.zel.impl.parser.AstValue.getTarget(AstValue.java:133) ~[zel-8.5.1.3.jar:8.5.1.3]
at org.zkoss.zel.impl.parser.AstValue.setValue(AstValue.java:216) ~[zel-8.5.1.3.jar:8.5.1.3]
at org.zkoss.zel.impl.ValueExpressionImpl.setValue(ValueExpressionImpl.java:260) ~[zel-8.5.1.3.jar:8.5.1.3]
at org.zkoss.zkmax.bind.impl.ValueExpressionImplEx.setValue(ValueExpressionImplEx.java:64) ~[zkmax-8.5.1.3.jar:?]
at org.zkoss.xel.zel.ELXelExpression.setValue(ELXelExpression.java:51) ~[zcommon-8.5.1.3.jar:8.5.1.3]
at org.zkoss.zkmax.bind.impl.BindEvaluatorXImplEx$LazyBindXelExpression.setValue(BindEvaluatorXImplEx.java:138) ~[zkmax-8.5.1.3.jar:?]
at org.zkoss.bind.impl.BindEvaluatorXImpl.setValue(BindEvaluatorXImpl.java:61) ~[zkbind-8.5.1.3.jar:8.5.1.3]
at org.zkoss.bind.impl.SavePropertyBindingImpl.save(SavePropertyBindingImpl.java:168) ~[zkbind-8.5.1.3.jar:8.5.1.3]
at org.zkoss.bind.impl.PropertyBindingHandler.doSaveBinding(PropertyBindingHandler.java:115) ~[zkbind-8.5.1.3.jar:8.5.1.3]
at org.zkoss.bind.impl.PropertyBindingHandler.doSaveEvent(PropertyBindingHandler.java:172) ~[zkbind-8.5.1.3.jar:8.5.1.3]
at org.zkoss.bind.impl.BinderImpl.doSaveEvent(BinderImpl.java:1899) ~[zkbind-8.5.1.3.jar:8.5.1.3]
at org.zkoss.bind.impl.BinderImpl.access$1100(BinderImpl.java:132) ~[zkbind-8.5.1.3.jar:8.5.1.3]
at org.zkoss.bind.impl.BinderImpl$CommandEventListener.onEvent0(BinderImpl.java:1590) ~[zkbind-8.5.1.3.jar:8.5.1.3]
at org.zkoss.bind.impl.BinderImpl$CommandEventListener.onEvent(BinderImpl.java:1558) ~[zkbind-8.5.1.3.jar:8.5.1.3]

User Story

As an app developer:

• I want to configure MVVM debug logging consistently so that logs are written in the desired files.
• I can enable logging on a specific package, so it won't print too many messages.
• I can know which component, the data binding expression, which page when this kind of error happens

Acceptance Criteria

logs are written into the configured files.

Details

currently the MVVM debug logs are written to console:
https://github.com/zkoss/zk/blob/27f90007e4d63638036b059da0ce2cd608b9b597/zkbind/src/org/zkoss/bind/sys/debugger/impl/DefaultExecutionInfoCollector.java#L128