当我尝试在域类上使用Groovy的JsonBuilder类时，我的Grails应用程序及其集成测试抛出StackOverflowError。我的代码是这样的:
String result = new JsonBuilder(new MyDomainClass())
因为我发现了关于JsonBuilder在自引用上循环的文章，所以我将域类剥离到几乎没有:
package com.mycompany.myapp.myarea
class MyDomainClass { }
但是堆栈溢出仍然会重新出现。问题来了。如果我将MyDomainClass的声明从其正常位置移到单元测试所在的文件中(即将其从其包中取出)，JsonBuilder就会工作。
下面的堆栈跟踪。有什么帮助吗?
谢谢,BGU
java.lang.StackOverflowError
at java.security.AccessController.doPrivileged(Native Method)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.createCallStaticSite(CallSiteArray.java:62)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.createCallSite(CallSiteArray.java:159)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:45)
at java_lang_Class$isArray.call(Unknown Source)
at groovy.json.JsonOutput.toJson(JsonOutput.groovy:135)
at groovy.json.JsonOutput$toJson.callStatic(Unknown Source)
at groovy.json.JsonOutput$_toJson_closure2.doCall(JsonOutput.groovy:158)
at sun.reflect.GeneratedMethodAccessor974.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:90)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:233)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1082)
at groovy.lang.ExpandoMetaClass.invokeMethod(ExpandoMetaClass.java:1106)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:906)
at groovy.lang.Closure.call(Closure.java:412)
at org.codehaus.groovy.runtime.DefaultGroovyMethods.callClosureForMapEntry(DefaultGroovyMethods.java:3870)
at org.codehaus.groovy.runtime.DefaultGroovyMethods.collect(DefaultGroovyMethods.java:2426)
at org.codehaus.groovy.runtime.DefaultGroovyMethods.collect(DefaultGroovyMethods.java:2443)
at org.codehaus.groovy.runtime.dgm$61.invoke(Unknown Source)
at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite$PojoMetaMethodSiteNoUnwrapNoCoerce.invoke(PojoMetaMethodSite.java:271)
at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite.call(PojoMetaMethodSite.java:53)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:116)
at groovy.json.JsonOutput.toJson(JsonOutput.groovy:154)
at groovy.json.JsonOutput$toJson$0.callStatic(Unknown Source)
at groovy.json.JsonOutput.toJson(JsonOutput.groovy:146)
at groovy.json.JsonOutput$toJson.callStatic(Unknown Source)
at groovy.json.JsonOutput$_toJson_closure1.doCall(JsonOutput.groovy:138)
at sun.reflect.GeneratedMethodAccessor978.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:90)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:233)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1082)
at groovy.lang.ExpandoMetaClass.invokeMethod(ExpandoMetaClass.java:1106)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:906)
at groovy.lang.Closure.call(Closure.java:412)
at groovy.lang.Closure.call(Closure.java:425)
at org.codehaus.groovy.runtime.DefaultGroovyMethods.collect(DefaultGroovyMethods.java:2157)
at org.codehaus.groovy.runtime.DefaultGroovyMethods.collect(DefaultGroovyMethods.java:2128)
at org.codehaus.groovy.runtime.dgm$59.invoke(Unknown Source)
at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite$PojoMetaMethodSiteNoUnwrapNoCoerce.invoke(PojoMetaMethodSite.java:271)
at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite.call(PojoMetaMethodSite.java:53)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:116)
at groovy.json.JsonOutput.toJson(JsonOutput.groovy:138)
at groovy.json.JsonOutput$toJson.callStatic(Unknown Source)
at groovy.json.JsonOutput$_toJson_closure2.doCall(JsonOutput.groovy:158)
at sun.reflect.GeneratedMethodAccessor974.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:90)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:233)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1082)
at groovy.lang.ExpandoMetaClass.invokeMethod(ExpandoMetaClass.java:1106)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:906)
at groovy.lang.Closure.call(Closure.java:412)
at org.codehaus.groovy.runtime.DefaultGroovyMethods.callClosureForMapEntry(DefaultGroovyMethods.java:3870)
at org.codehaus.groovy.runtime.DefaultGroovyMethods.collect(DefaultGroovyMethods.java:2426)
at org.codehaus.groovy.runtime.DefaultGroovyMethods.collect(DefaultGroovyMethods.java:2443)
at org.codehaus.groovy.runtime.dgm$61.invoke(Unknown Source)
at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite$PojoMetaMethodSiteNoUnwrapNoCoerce.invoke(PojoMetaMethodSite.java:271)
at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite.call(PojoMetaMethodSite.java:53)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:116)
at groovy.json.JsonOutput.toJson(JsonOutput.groovy:154)
at groovy.json.JsonOutput$toJson$0.callStatic(Unknown Source)
at groovy.json.JsonOutput.toJson(JsonOutput.groovy:146)
at groovy.json.JsonOutput$toJson.callStatic(Unknown Source)
at groovy.json.JsonOutput$_toJson_closure1.doCall(JsonOutput.groovy:138)
at sun.reflect.GeneratedMethodAccessor978.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:90)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:233)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1082)
at groovy.lang.ExpandoMetaClass.invokeMethod(ExpandoMetaClass.java:1106)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:906)
at groovy.lang.Closure.call(Closure.java:412)
at groovy.lang.Closure.call(Closure.java:425)
at org.codehaus.groovy.runtime.DefaultGroovyMethods.collect(DefaultGroovyMethods.java:2157)
at org.codehaus.groovy.runtime.DefaultGroovyMethods.collect(DefaultGroovyMethods.java:2128)
at org.codehaus.groovy.runtime.dgm$59.invoke(Unknown Source)
at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite$PojoMetaMethodSiteNoUnwrapNoCoerce.invoke(PojoMetaMethodSite.java:271)
at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite.call(PojoMetaMethodSite.java:53)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:116)
at groovy.json.JsonOutput.toJson(JsonOutput.groovy:138)
at groovy.json.JsonOutput$toJson.callStatic(Unknown Source)
at groovy.json.JsonOutput$_toJson_closure2.doCall(JsonOutput.groovy:158)
at sun.reflect.GeneratedMethodAccessor974.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:90)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:233)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1082)
at groovy.lang.ExpandoMetaClass.invokeMethod(ExpandoMetaClass.java:1106)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:906)
at groovy.lang.Closure.call(Closure.java:412)
at org.codehaus.groovy.runtime.DefaultGroovyMethods.callClosureForMapEntry(DefaultGroovyMethods.java:3870)
at org.codehaus.groovy.runtime.DefaultGroovyMethods.collect(DefaultGroovyMethods.java:2426)
at org.codehaus.groovy.runtime.DefaultGroovyMethods.collect(DefaultGroovyMethods.java:2443)
at org.codehaus.groovy.runtime.dgm$61.invoke(Unknown Source)
at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite$PojoMetaMethodSiteNoUnwrapNoCoerce.invoke(PojoMetaMethodSite.java:271)
at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite.call(PojoMetaMethodSite.java:53)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:116)
at groovy.json.JsonOutput.toJson(JsonOutput.groovy:154)
at groovy.json.JsonOutput$toJson$0.callStatic(Unknown Source)
at groovy.json.JsonOutput.toJson(JsonOutput.groovy:146)
at groovy.json.JsonOutput$toJson.callStatic(Unknown Source)
at groovy.json.JsonOutput$_toJson_closure1.doCall(JsonOutput.groovy:138)
at sun.reflect.GeneratedMethodAccessor978.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:90)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:233)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1082)
at groovy.lang.ExpandoMetaClass.invokeMethod(ExpandoMetaClass.java:1106)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:906)
at groovy.lang.Closure.call(Closure.java:412)
at groovy.lang.Closure.call(Closure.java:425)
at org.codehaus.groovy.runtime.DefaultGroovyMethods.collect(DefaultGroovyMethods.java:2157)
at org.codehaus.groovy.runtime.DefaultGroovyMethods.collect(DefaultGroovyMethods.java:2128)
at org.codehaus.groovy.runtime.dgm$59.invoke(Unknown Source)
at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite$PojoMetaMethodSiteNoUnwrapNoCoerce.invoke(PojoMetaMethodSite.java:271)
at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite.call(PojoMetaMethodSite.java:53)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:116)
at groovy.json.JsonOutput.toJson(JsonOutput.groovy:138)
at groovy.json.JsonOutput$toJson.callStatic(Unknown Source)
at groovy.json.JsonOutput$_toJson_closure2.doCall(JsonOutput.groovy:158)
at sun.reflect.GeneratedMethodAccessor974.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:90)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:233)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1082)
at groovy.lang.ExpandoMetaClass.invokeMethod(ExpandoMetaClass.java:1106)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:906)
at groovy.lang.Closure.call(Closure.java:412)
at org.codehaus.groovy.runtime.DefaultGroovyMethods.callClosureForMapEntry(DefaultGroovyMethods.java:3870)
at org.codehaus.groovy.runtime.DefaultGroovyMethods.collect(DefaultGroovyMethods.java:2426)
at org.codehaus.groovy.runtime.DefaultGroovyMethods.collect(DefaultGroovyMethods.java:2443)
at org.codehaus.groovy.runtime.dgm$61.invoke(Unknown Source)
at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite$PojoMetaMethodSiteNoUnwrapNoCoerce.invoke(PojoMetaMethodSite.java:271)...
我稍微深入了一下代码，JsonBuilder有许多类型检查来决定应该如何编写对象。在域类的情况下，它匹配Iterable。然后，它尝试遍历它并写入每一项，等等。
奇怪的是next在将对象转换为Iterable后返回对象本身....
如果我写下面的代码(没有显式强制转换仍然失败)，它可以工作:
String result = new JsonBuilder((Map)(new MyDomainClass().properties))