StreamingMarkupBuilder.out 将 'it' 评估为命名空间前缀答案

【问题标题】：StreamingMarkupBuilder.out evaluates 'it' as a namespace prefixStreamingMarkupBuilder.out 将 'it' 评估为命名空间前缀
【发布时间】：2013-07-19 19:41:18
【问题描述】：

我正在尝试使用以下代码从自定义 Artifact groovy 类生成一个 pom：

def outputBuilder = new StreamingMarkupBuilder()

    List<Artifact> artifacts = []
    artifacts << new Artifact(groupId: "g", artifactId: "a", version: "v")
    artifacts << new Artifact(groupId: "g1", artifactId: "a1", version: "v1")

    def pom = {
        project() {
            modelVersion("4.0.0")
            groupId("gi")
            artifactId("ai")
            version("007")
            packaging("pom")
            dependencyManagement() {
                out <<
                        artifacts.each {
                            dependency {
                                groupId(it.groupId)
                            }
                        }
            }
        }
    }

    println outputBuilder.bind(pom)
}

运行这个简单的例子会产生这个错误：

Exception in thread "main" groovy.lang.GroovyRuntimeException: Namespace prefix: groupId is not bound to a URI
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at org.codehaus.groovy.reflection.CachedConstructor.invoke(CachedConstructor.java:77)
at org.codehaus.groovy.reflection.CachedConstructor.doConstructorInvoke(CachedConstructor.java:71)
at org.codehaus.groovy.runtime.callsite.ConstructorSite$ConstructorSiteNoUnwrap.callConstructor(ConstructorSite.java:81)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallConstructor(CallSiteArray.java:57)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callConstructor(AbstractCallSite.java:182)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callConstructor(AbstractCallSite.java:190)
at groovy.xml.StreamingMarkupBuilder$_closure6.doCall(StreamingMarkupBuilder.groovy:130)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:90)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:233)
at org.codehaus.groovy.runtime.metaclass.ClosureMetaClass.invokeMethod(ClosureMetaClass.java:272)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:909)
at groovy.lang.Closure.call(Closure.java:411)
at groovy.xml.streamingmarkupsupport.BaseMarkupBuilder$Document.invokeMethod(BaseMarkupBuilder.java:148)
at org.codehaus.groovy.runtime.metaclass.ClosureMetaClass.invokeOnDelegationObjects(ClosureMetaClass.java:423)
at org.codehaus.groovy.runtime.metaclass.ClosureMetaClass.invokeMethod(ClosureMetaClass.java:346)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:909)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:730)
at groovy.lang.GroovyObjectSupport.invokeMethod(GroovyObjectSupport.java:44)
at org.codehaus.groovy.runtime.metaclass.ClosureMetaClass.invokeOnDelegationObjects(ClosureMetaClass.java:407)
at org.codehaus.groovy.runtime.metaclass.ClosureMetaClass.invokeMethod(ClosureMetaClass.java:346)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:909)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:730)
at groovy.lang.GroovyObjectSupport.invokeMethod(GroovyObjectSupport.java:44)
at org.codehaus.groovy.runtime.metaclass.ClosureMetaClass.invokeOnDelegationObjects(ClosureMetaClass.java:407)
at org.codehaus.groovy.runtime.metaclass.ClosureMetaClass.invokeMethod(ClosureMetaClass.java:346)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:909)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:730)
at groovy.lang.GroovyObjectSupport.invokeMethod(GroovyObjectSupport.java:44)
at org.codehaus.groovy.runtime.metaclass.ClosureMetaClass.invokeOnDelegationObjects(ClosureMetaClass.java:407)
at org.codehaus.groovy.runtime.metaclass.ClosureMetaClass.invokeMethod(ClosureMetaClass.java:346)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:909)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:730)
at groovy.lang.GroovyObjectSupport.invokeMethod(GroovyObjectSupport.java:44)
at org.codehaus.groovy.runtime.metaclass.ClosureMetaClass.invokeOnDelegationObjects(ClosureMetaClass.java:407)
at org.codehaus.groovy.runtime.metaclass.ClosureMetaClass.invokeMethod(ClosureMetaClass.java:346)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:909)
at org.codehaus.groovy.runtime.callsite.PogoMetaClassSite.callCurrent(PogoMetaClassSite.java:66)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallCurrent(CallSiteArray.java:49)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:133)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:141)

一旦我将groupId(it.groupId) 更改为groupId("XXX")，pom 就可以正常打印了。

我怎样才能“欺骗 groovy”来评估迭代器变量 groupId 而不是将其评估为缺少的命名空间前缀。 groupId("$it.groupId") 等都没用。

【问题讨论】：

标签： groovy markupbuilder

【解决方案1】：

it 是周围闭包的隐式变量。在您的情况下，it 代表闭包 dependency{} 的隐式变量，这是不正确的。你的意思是it 是一个变量，代表来自artifacts 的每个工件。

解决方法，使用如下：

....
artifacts.each{ar -> 
    dependency{
        groupId(ar.groupId)
    }
}
......

【讨论】：