SchemaFactory 不支持平台级别 8 中的 W3C XML Schema? [英] SchemaFactory doesn't support W3C XML Schema in platform level 8?
问题描述
使用 Android SDK，纯空 Activity 中的以下代码会失败:
With the Android SDK, the following code in a plain empty Activity fails:
@Override
protected void onStart() {
super.onStart();
SchemaFactory schemaFactory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
}
2.2 模拟器 logcat 显示此异常:
The 2.2 emulator logcat shows this exception:
06-28 05:38:06.107: WARN/dalvikvm(495): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
06-28 05:38:06.128: ERROR/AndroidRuntime(495): FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example/com.example.HelloWorldActivity}: java.lang.IllegalArgumentException: http://www.w3.org/2001/XMLSchema
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
at android.app.ActivityThread.access$2300(ActivityThread.java:125)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:123)
at android.app.ActivityThread.main(ActivityThread.java:4627)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:521)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.IllegalArgumentException: http://www.w3.org/2001/XMLSchema
at javax.xml.validation.SchemaFactory.newInstance(SchemaFactory.java:194)
at com.example.HelloWorldActivity.onStart(HelloWorldActivity.java:26)
at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1129)
at android.app.Activity.performStart(Activity.java:3781)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2636)
... 11 more
SchemaFactory的Javadoc 提到平台默认 SchemaFactory 以特定于实现的方式定位.W3C XML Schema 必须有一个平台默认 SchemaFactory."
The Javadoc of SchemaFactory mentions "Platform default SchemaFactory is located in a implementation specific way. There must be a platform default SchemaFactory for W3C XML Schema."
推荐答案
我遇到了同样的问题并阅读了很多帖子，然后才得到适合我的答案.对常量的引用在 Dalvik 上不起作用.我发现我必须修改我的代码才能使用 Xerces-for-Android 项目，然后我才能获得我所追求的 xml 验证.这很可能是您通过变量引用所做的事情.以下是设置的详细信息和一些示例代码，展示了如何让验证在 android 上运行.
I had the same problem and read many posts before I got an answer that worked for me. The reference to the constant won't work on Dalvik. I found I had to modify my code to work with the Xerces-for-Android project then I was able to get the xml validation I was after. Which is most likely what you are doing by the variable reference. The following are details of the setup and some example code showing how to get the validation to work on android.
以下内容对我有用:
- 创建验证实用程序.
- 将 xml 和 xsd 都放入 android 操作系统上的文件中，并针对它使用验证实用程序.
- 使用 Xerces-For-Android 进行验证.
Android 确实支持一些我们可以使用的包，我创建了基于以下内容的 xml 验证实用程序:http://docs.oracle.com/javase/1.5.0/docs/api/javax/xml/validation/package-summary.html
Android does support some packages which we can use, I created my xml validation utility based on: http://docs.oracle.com/javase/1.5.0/docs/api/javax/xml/validation/package-summary.html
我最初的沙盒测试使用 java 非常顺利，然后我尝试将其移植到 Dalvik 并发现我的代码不起作用.Dalvik 不支持某些东西，所以我做了一些修改.
My initial sandbox testing was pretty smooth with java, then I tried to port it over to Dalvik and found that my code did not work. Some things just aren't supported the same with Dalvik, so I made some modifications.
我找到了对 android 的 xerces 的引用，因此我修改了我的沙盒测试(以下不适用于 android，之后的示例可以):
I found a reference to xerces for android, so I modified my sandbox test of (the following doesn't work with android, the example after this does):
import java.io.File;
import javax.xml.XMLConstants;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.Source;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamSource;
import javax.xml.validation.Schema;
import javax.xml.validation.SchemaFactory;
import javax.xml.validation.Validator;
import org.w3c.dom.Document;
/**
* A Utility to help with xml communication validation.
*/
public class XmlUtil {
/**
* Validation method.
* Base code/example from: http://docs.oracle.com/javase/1.5.0/docs/api/javax/xml/validation/package-summary.html
*
* @param xmlFilePath The xml file we are trying to validate.
* @param xmlSchemaFilePath The schema file we are using for the validation. This method assumes the schema file is valid.
* @return True if valid, false if not valid or bad parse.
*/
public static boolean validate(String xmlFilePath, String xmlSchemaFilePath) {
// parse an XML document into a DOM tree
DocumentBuilder parser = null;
Document document;
// Try the validation, we assume that if there are any issues with the validation
// process that the input is invalid.
try {
// validate the DOM tree
parser = DocumentBuilderFactory.newInstance().newDocumentBuilder();
document = parser.parse(new File(xmlFilePath));
// create a SchemaFactory capable of understanding WXS schemas
SchemaFactory factory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
// load a WXS schema, represented by a Schema instance
Source schemaFile = new StreamSource(new File(xmlSchemaFilePath));
Schema schema = factory.newSchema(schemaFile);
// create a Validator instance, which can be used to validate an instance document
Validator validator = schema.newValidator();
validator.validate(new DOMSource(document));
} catch (Exception e) {
// Catches: SAXException, ParserConfigurationException, and IOException.
return false;
}
return true;
}
}
上面的代码必须进行一些修改才能与 xerces for android (http://gc.codehum.com/p/xerces-for-android/).获取项目需要SVN，以下是一些crib note:
The above code had to be modified some to work with xerces for android (http://gc.codehum.com/p/xerces-for-android/). You need SVN to get the project, the following are some crib notes:
download xerces-for-android
download silk svn (for windows users) from http://www.sliksvn.com/en/download
install silk svn (I did complete install)
Once the install is complete, you should have svn in your system path.
Test by typing "svn" from the command line.
I went to my desktop then downloaded the xerces project by:
svn checkout http://xerces-for-android.googlecode.com/svn/trunk/ xerces-for-android-read-only
You should then have a new folder on your desktop called xerces-for-android-read-only
使用上面的jar(最后我会做成jar，直接复制到我的源码中进行快速测试.如果你想这样做，你可以用Ant快速制作jar(http://ant.apache.org/manual/using.html))，我能够得到以下内容适用于我的 xml 验证:
With the above jar (Eventually I'll make it into a jar, just copied it directly into my source for quick testing. If you wish to do the same, you can making the jar quickly with Ant (http://ant.apache.org/manual/using.html)), I was able to get the following to work for my xml validation:
import java.io.File;
import java.io.IOException;
import mf.javax.xml.transform.Source;
import mf.javax.xml.transform.stream.StreamSource;
import mf.javax.xml.validation.Schema;
import mf.javax.xml.validation.SchemaFactory;
import mf.javax.xml.validation.Validator;
import mf.org.apache.xerces.jaxp.validation.XMLSchemaFactory;
import org.xml.sax.SAXException;
/**
* A Utility to help with xml communication validation.
*/public class XmlUtil {
/**
* Validation method.
*
* @param xmlFilePath The xml file we are trying to validate.
* @param xmlSchemaFilePath The schema file we are using for the validation. This method assumes the schema file is valid.
* @return True if valid, false if not valid or bad parse or exception/error during parse.
*/
public static boolean validate(String xmlFilePath, String xmlSchemaFilePath) {
// Try the validation, we assume that if there are any issues with the validation
// process that the input is invalid.
try {
SchemaFactory factory = new XMLSchemaFactory();
Source schemaFile = new StreamSource(new File(xmlSchemaFilePath));
Source xmlSource = new StreamSource(new File(xmlFilePath));
Schema schema = factory.newSchema(schemaFile);
Validator validator = schema.newValidator();
validator.validate(xmlSource);
} catch (SAXException e) {
return false;
} catch (IOException e) {
return false;
} catch (Exception e) {
// Catches everything beyond: SAXException, and IOException.
e.printStackTrace();
return false;
} catch (Error e) {
// Needed this for debugging when I was having issues with my 1st set of code.
e.printStackTrace();
return false;
}
return true;
}
}
一些旁注:
为了创建文件，我制作了一个简单的文件实用程序来将字符串写入文件:
For creating the files, I made a simple file utility to write string to files:
public static void createFileFromString(String fileText, String fileName) {
try {
File file = new File(fileName);
BufferedWriter output = new BufferedWriter(new FileWriter(file));
output.write(fileText);
output.close();
} catch ( IOException e ) {
e.printStackTrace();
}
}
我还需要写一个我可以访问的区域，所以我使用了:
I also needed to write to an area that I had access to, so I made use of:
String path = this.getActivity().getPackageManager().getPackageInfo(getPackageName(), 0).applicationInfo.dataDir;
有点hackish，它有效.我确信有更简洁的方法可以做到这一点，但我想我会分享我的成功，因为我没有找到任何好的例子.
A little hackish, it works. I'm sure there is a more succinct way of doing this, however I figured I'd share my success, as there weren't any good examples that I found.
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