关于import导入库的问题

Question

我用import 导入了一个库：
  import com.sun.org.apache.xerces.internal.parsers.DOMParser;
程序可以使用类DOMParser，但是我在java sdk文档中找不到这个类的定义，这是为什么呢？

Answer 1

package com.sun.org.apache.xerces.internal.parsers;import java.io.IOException;import com.sun.org.apache.xerces.internal.impl.Constants;
import com.sun.org.apache.xerces.internal.util.EntityResolverWrapper;
import com.sun.org.apache.xerces.internal.util.EntityResolver2Wrapper;
import com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper;
import com.sun.org.apache.xerces.internal.util.SAXMessageFormatter;
import com.sun.org.apache.xerces.internal.util.SymbolTable;
import com.sun.org.apache.xerces.internal.xni.XNIException;
import com.sun.org.apache.xerces.internal.xni.grammars.XMLGrammarPool;
import com.sun.org.apache.xerces.internal.xni.parser.XMLConfigurationException;
import com.sun.org.apache.xerces.internal.xni.parser.XMLEntityResolver;
import com.sun.org.apache.xerces.internal.xni.parser.XMLErrorHandler;
import com.sun.org.apache.xerces.internal.xni.parser.XMLInputSource;
import com.sun.org.apache.xerces.internal.xni.parser.XMLParseException;
import com.sun.org.apache.xerces.internal.xni.parser.XMLParserConfiguration;
import org.w3c.dom.Node;
import org.xml.sax.EntityResolver;
import org.xml.sax.ErrorHandler;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.SAXNotRecognizedException;
import org.xml.sax.SAXNotSupportedException;
import org.xml.sax.SAXParseException;
import org.xml.sax.ext.EntityResolver2;
import org.xml.sax.helpers.LocatorImpl;/**
 * This is the main Xerces DOM parser class. It uses the abstract DOM
 * parser with a document scanner, a dtd scanner, and a validator, as
 * well as a grammar pool.
 *
 * @author Arnaud  Le Hors, IBM
 * @author Andy Clark, IBM
 *
 * @version $Id: DOMParser.java,v 1.2.6.1 2005/09/06 13:06:37 sunithareddy Exp $
 */
public class DOMParser
    extends AbstractDOMParser {    //
    // Constants
    //
    
    // features
    
    /** Feature identifier: EntityResolver2. */
    protected static final String USE_ENTITY_RESOLVER2 =
        Constants.SAX_FEATURE_PREFIX + Constants.USE_ENTITY_RESOLVER2_FEATURE;    // properties    /** Property identifier: symbol table. */
    protected static final String SYMBOL_TABLE =
        Constants.XERCES_PROPERTY_PREFIX + Constants.SYMBOL_TABLE_PROPERTY;    /** Property identifier: XML grammar pool. */
    protected static final String XMLGRAMMAR_POOL =
        Constants.XERCES_PROPERTY_PREFIX+Constants.XMLGRAMMAR_POOL_PROPERTY;    /** Recognized properties. */
    private static final String[] RECOGNIZED_PROPERTIES = {
        SYMBOL_TABLE,
        XMLGRAMMAR_POOL,
    };
    
    //
    // Data
    //
    
    // features
    
    /** Use EntityResolver2. */
    protected boolean fUseEntityResolver2 = true;    //
    // Constructors
    //    /**
     * Constructs a DOM parser using the specified parser configuration.
     */
    public DOMParser(XMLParserConfiguration config) {
        super(config);
    } // <init>(XMLParserConfiguration)    /**
     * Constructs a DOM parser using the dtd/xml schema parser configuration.
     */
    public DOMParser() {
        this(null, null);
    } // <init>()    /**
     * Constructs a DOM parser using the specified symbol table.
     */
    public DOMParser(SymbolTable symbolTable) {
        this(symbolTable, null);
    } // <init>(SymbolTable)
    /**
     * Constructs a DOM parser using the specified symbol table and
     * grammar pool.
     */
    public DOMParser(SymbolTable symbolTable, XMLGrammarPool grammarPool) {
        super((XMLParserConfiguration)ObjectFactory.createObject(
            "com.sun.org.apache.xerces.internal.xni.parser.XMLParserConfiguration",
            "com.sun.org.apache.xerces.internal.parsers.XIncludeAwareParserConfiguration"
            ));        // set properties
        fConfiguration.addRecognizedProperties(RECOGNIZED_PROPERTIES);
        if (symbolTable != null) {
            fConfiguration.setProperty(SYMBOL_TABLE, symbolTable);
        }
        if (grammarPool != null) {
            fConfiguration.setProperty(XMLGRAMMAR_POOL, grammarPool);
        }    } // <init>(SymbolTable,XMLGrammarPool)    //
    // XMLReader methods
    //    /**
     * Parses the input source specified by the given system identifier.
     * <p>
     * This method is equivalent to the following:
     * <pre>
     *     parse(new InputSource(systemId));
     * </pre>
     *
     * @param systemId The system identifier (URI).
     *
     * @exception org.xml.sax.SAXException Throws exception on SAX error.
     * @exception java.io.IOException Throws exception on i/o error.
     */
    public void parse(String systemId) throws SAXException, IOException {        // parse document
        XMLInputSource source = new XMLInputSource(null, systemId, null);
        try {
            parse(source);
        }        // wrap XNI exceptions as SAX exceptions
        catch (XMLParseException e) {
            Exception ex = e.getException();
            if (ex == null) {
                // must be a parser exception; mine it for locator info and throw
                // a SAXParseException
                LocatorImpl locatorImpl = new LocatorImpl();
                locatorImpl.setPublicId(e.getPublicId());
                locatorImpl.setSystemId(e.getExpandedSystemId());
                locatorImpl.setLineNumber(e.getLineNumber());
                locatorImpl.setColumnNumber(e.getColumnNumber());
                throw new SAXParseException(e.getMessage(), locatorImpl);
            }
            if (ex instanceof SAXException) {
                // why did we create an XMLParseException?
                throw (SAXException)ex;
            }
            if (ex instanceof IOException) {
                throw (IOException)ex;
            }
            throw new SAXException(ex);
        }
        catch (XNIException e) {
            e.printStackTrace();
            Exception ex = e.getException();
            if (ex == null) {
                throw new SAXException(e.getMessage());
            }
            if (ex instanceof SAXException) {
                throw (SAXException)ex;
            }
            if (ex instanceof IOException) {
                throw (IOException)ex;
            }
            throw new SAXException(ex);
        }    } // parse(String)

Answer 2

/**
     * parse
     *
     * @param inputSource
     *
     * @exception org.xml.sax.SAXException
     * @exception java.io.IOException
     */
    public void parse(InputSource inputSource)
        throws SAXException, IOException {        // parse document
        try {
            XMLInputSource xmlInputSource =
                new XMLInputSource(inputSource.getPublicId(),
                                   inputSource.getSystemId(),
                                   null);
            xmlInputSource.setByteStream(inputSource.getByteStream());
            xmlInputSource.setCharacterStream(inputSource.getCharacterStream());
            xmlInputSource.setEncoding(inputSource.getEncoding());
            parse(xmlInputSource);
        }        // wrap XNI exceptions as SAX exceptions
        catch (XMLParseException e) {
            Exception ex = e.getException();
            if (ex == null) {
                // must be a parser exception; mine it for locator info and throw
                // a SAXParseException
                LocatorImpl locatorImpl = new LocatorImpl();
                locatorImpl.setPublicId(e.getPublicId());
                locatorImpl.setSystemId(e.getExpandedSystemId());
                locatorImpl.setLineNumber(e.getLineNumber());
                locatorImpl.setColumnNumber(e.getColumnNumber());
                throw new SAXParseException(e.getMessage(), locatorImpl);
            }
            if (ex instanceof SAXException) {
                // why did we create an XMLParseException?
                throw (SAXException)ex;
            }
            if (ex instanceof IOException) {
                throw (IOException)ex;
            }
            throw new SAXException(ex);
        }
        catch (XNIException e) {
            Exception ex = e.getException();
            if (ex == null) {
                throw new SAXException(e.getMessage());
            }
            if (ex instanceof SAXException) {
                throw (SAXException)ex;
            }
            if (ex instanceof IOException) {
                throw (IOException)ex;
            }
            throw new SAXException(ex);
        }    } // parse(InputSource)    /**
     * Sets the resolver used to resolve external entities. The EntityResolver
     * interface supports resolution of public and system identifiers.
     *
     * @param resolver The new entity resolver. Passing a null value will
     *                 uninstall the currently installed resolver.
     */
    public void setEntityResolver(EntityResolver resolver) {        try {
            XMLEntityResolver xer = (XMLEntityResolver) fConfiguration.getProperty(ENTITY_RESOLVER);
            if (fUseEntityResolver2 && resolver instanceof EntityResolver2) {
                if (xer instanceof EntityResolver2Wrapper) {
                    EntityResolver2Wrapper er2w = (EntityResolver2Wrapper) xer;
                    er2w.setEntityResolver((EntityResolver2) resolver);
                }
                else {
                    fConfiguration.setProperty(ENTITY_RESOLVER,
                            new EntityResolver2Wrapper((EntityResolver2) resolver));
                }
            }
            else {
                if (xer instanceof EntityResolverWrapper) {
                    EntityResolverWrapper erw = (EntityResolverWrapper) xer;
                    erw.setEntityResolver(resolver);
                }
                else {
                    fConfiguration.setProperty(ENTITY_RESOLVER,
                            new EntityResolverWrapper(resolver));
                }
            }
        }
        catch (XMLConfigurationException e) {
            // do nothing
        }    } // setEntityResolver(EntityResolver)    /**
     * Return the current entity resolver.
     *
     * @return The current entity resolver, or null if none
     *         has been registered.
     * @see #setEntityResolver
     */
    public EntityResolver getEntityResolver() {        EntityResolver entityResolver = null;
        try {
            XMLEntityResolver xmlEntityResolver =
                (XMLEntityResolver)fConfiguration.getProperty(ENTITY_RESOLVER);
            if (xmlEntityResolver != null) {
                if (xmlEntityResolver instanceof EntityResolverWrapper) {
                    entityResolver =
                        ((EntityResolverWrapper) xmlEntityResolver).getEntityResolver();
                }
                else if (xmlEntityResolver instanceof EntityResolver2Wrapper) {
                    entityResolver = 
                        ((EntityResolver2Wrapper) xmlEntityResolver).getEntityResolver();
                }
            }
        }
        catch (XMLConfigurationException e) {
            // do nothing
        }
        return entityResolver;    } // getEntityResolver():EntityResolver    /**
     * Allow an application to register an error event handler.
     *
     * <p>If the application does not register an error handler, all
     * error events reported by the SAX parser will be silently
     * ignored; however, normal processing may not continue.  It is
     * highly recommended that all SAX applications implement an
     * error handler to avoid unexpected bugs.</p>
     *
     * <p>Applications may register a new or different handler in the
     * middle of a parse, and the SAX parser must begin using the new
     * handler immediately.</p>
     *
     * @param errorHandler The error handler.
     * @exception java.lang.NullPointerException If the handler
     *            argument is null.
     * @see #getErrorHandler
     */
    public void setErrorHandler(ErrorHandler errorHandler) {        try {
            XMLErrorHandler xeh = (XMLErrorHandler) fConfiguration.getProperty(ERROR_HANDLER);
            if (xeh instanceof ErrorHandlerWrapper) {
                ErrorHandlerWrapper ehw = (ErrorHandlerWrapper) xeh;
                ehw.setErrorHandler(errorHandler);
            }
            else {
                fConfiguration.setProperty(ERROR_HANDLER,
                        new ErrorHandlerWrapper(errorHandler));
            }
        }
        catch (XMLConfigurationException e) {
            // do nothing
        }    } // setErrorHandler(ErrorHandler)

Answer 3

在默认jdk里都有
在你没删的前提下,

Answer 4

这个包存在于apche服务器中，你把网线拔了你看还能导入吗？明白了吧！

Answer 5

难道说在使用这个包的时候还需要启动apache吗？我使了以下不用呀。
如果在默认jdk中都有的话为什么帮助文挡中确没有呢？