默认的 xpath 可以不使用 namespace。
例如使用下面的代码进行 xpath 查询。
XPathExpression<Element> xPath = XPathFactory.instance().compile(
"/Amazon:ItemLookupResponse/Amazon:Items/Amazon:Item/Amazon:ItemAttributes", Filters.element());
如果使用 namespace ，则需要使用下面的代码，否则将会出现错误：
java.lang.RuntimeException: java.lang.IllegalArgumentException: Namespace with prefix 'Amazon' has not been declared.
at com.bcodepot.datacrawl.api.Amazon.getMerchandise(Amazon.java:406)
at com.bcodepot.datacrawl.test.AmazonTest.testBatchUPC(AmazonTest.java:269)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
Caused by: java.lang.IllegalArgumentException: Namespace with prefix 'Amazon' has not been declared.
at org.jdom2.xpath.util.AbstractXPathCompiled.getNamespace(AbstractXPathCompiled.java:256)
at org.jdom2.xpath.jaxen.JaxenCompiled.translateNamespacePrefixToUri(JaxenCompiled.java:171)
at org.jaxen.ContextSupport.translateNamespacePrefixToUri(ContextSupport.java:190)
at org.jaxen.expr.DefaultNameStep.matches(DefaultNameStep.java:356)
at org.jaxen.expr.DefaultNameStep.evaluate(DefaultNameStep.java:209)
at org.jaxen.expr.DefaultLocationPath.evaluate(DefaultLocationPath.java:140)
at org.jaxen.expr.DefaultAbsoluteLocationPath.evaluate(DefaultAbsoluteLocationPath.java:113)
at org.jaxen.expr.DefaultXPathExpr.asList(DefaultXPathExpr.java:102)
at org.jaxen.BaseXPath.selectNodesForContext(BaseXPath.java:677)
at org.jaxen.BaseXPath.selectNodes(BaseXPath.java:216)
at org.jdom2.xpath.jaxen.JaxenCompiled.evaluateRawAll(JaxenCompiled.java:198)
at org.jdom2.xpath.util.AbstractXPathCompiled.evaluate(AbstractXPathCompiled.java:356)
at com.bcodepot.datacrawl.api.Amazon.getMerchandise(Amazon.java:383)
... 24 more
修改后的代码如下：
[code]Namespace amazonNamespace = Namespace.getNamespace(“Amazon”, “http://webservices.amazon.com/AWSECommerceService/2011-08-01”);
XPathExpression<Element> xPath = XPathFactory.instance().compile("/Amazon:ItemLookupResponse/Amazon:Items/Amazon:Item/Amazon:ItemAttributes", Filters.element(), null,
amazonNamespace);[/code]