Java与XQuery在BaseX集成中的实践指南

package com.linghu.util;
import java.io.*;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.nio.charset.Charset;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.ArrayList;
/**
 * Java client for BaseX.
 * Works with BaseX 7.0 and later
 *
 * Documentation: https://docs.basex.org/wiki/Clients
 *
 * (C) BaseX Team 2005-22, BSD License
 */
public final class BaseXClient implements Closeable {
    /** UTF-8 charset. */
    private static final Charset UTF8 = Charset.forName("UTF-8");
    /** Output stream. */
    private final OutputStream out;
    /** Input stream (buffered). */
    private final BufferedInputStream in;
    /** Socket. */
    private final Socket socket;
    /** Command info. */
    private String info;
    /**
     * Constructor.
     * @param host server name
     * @param port server port
     * @param username user name
     * @param password password
     * @throws
     */
    public BaseXClient(final String host, final int port, final String username,
                       final String password) throws IOException {
        socket = new Socket();
        socket.setTcpNoDelay(true);
        socket.connect(new InetSocketAddress(host, port), 5000);
        in = new BufferedInputStream(socket.getInputStream());
        out = socket.getOutputStream();
        // receive server response
        final String[] response = receive().split(":");
        final String code, nonce;
        if(response.length > 1) {
            // support for digest authentication
            code = username + ':' + response[0] + ':' + password;
            nonce = response[1];
        } else {
            // support for cram-md5 (Version < 8.0)
            code = password;
            nonce = response[0];
        }
        send(username);
        send(md5(md5(code) + nonce));
        // receive success flag
        if(!ok()) throw new IOException("Access denied.");
    }
    /**
     * Executes a command and serializes the result to an output stream.
     * @param command command
     * @param output output stream
     * @throws IOException Exception
     */
    public void execute(final String command, final OutputStream output) throws IOException {
        // send {Command}0
        send(command);
        receive(in, output);
        info = receive();
        if(!ok()) throw new IOException(info);
    }
    /**
     * Executes a command and returns the result.
     * @param command command
     * @return result
     * @throws IOException Exception
     */
    public String execute(final String command) throws IOException {
        final ByteArrayOutputStream os = new ByteArrayOutputStream();
        execute(command, os);
        return new String(os.toByteArray(), UTF8);
    }
    /**
     * Creates a query object.
     * @param query query string
     * @return query
     * @throws IOException Exception
     */
    public Query query(final String query) throws IOException {
        return new Query(query);
    }
    /**
     * Creates a database.
     * @param name name of database
     * @param input xml input
     * @throws IOException I/O exception
     */
    public void create(final String name, final InputStream input) throws IOException {
        send(8, name, input);
    }
    /**
     * Adds a document to a database.
     * @param path path to resource
     * @param input xml input
     * @throws IOException I/O exception
     */
    public void add(final String path, final InputStream input) throws IOException {
        send(9, path, input);
    }
    /**
     * Replaces a document in a database.
     * @param path path to resource
     * @param input xml input
     * @throws IOException I/O exception
     */
    public void replace(final String path, final InputStream input) throws IOException {
        send(12, path, input);
    }
    /**
     * Stores a binary resource in a database.
     * @param path path to resource
     * @param input xml input
     * @throws IOException I/O exception
     */
    public void store(final String path, final InputStream input) throws IOException {
        send(13, path, input);
    }
    /**
     * Returns command information.
     * @return string info
     */
    public String info() {
        return info;
    }
    /**
     * Closes the session.
     * @throws IOException Exception
     */
    @Override
    public void close() throws IOException, IOException {
        send("exit");
        out.flush();
        socket.close();
    }
    /**
     * Checks the next success flag.
     * @return value of check
     * @throws IOException Exception
     */
    private boolean ok() throws IOException {
        out.flush();
        return in.read() == 0;
    }
    /**
     * Returns the next received string.
     * @return String result or info
     * @throws IOException I/O exception
     */
    private String receive() throws IOException {
        final ByteArrayOutputStream os = new ByteArrayOutputStream();
        receive(in, os);
        return new String(os.toByteArray(), UTF8);
    }
    /**
     * Sends a string to the server.
     * @param string string to be sent
     * @throws IOException I/O exception
     */
    private void send(final String string) throws IOException {
        out.write((string + '\0').getBytes(UTF8));
    }
    /**
     * Receives a string and writes it to the specified output stream.
     * @param input input stream
     * @param output output stream
     * @throws IOException I/O exception
     */
    private static void receive(final InputStream input, final OutputStream output)
            throws IOException {
        for(int b; (b = input.read()) > 0;) {
            // read next byte if 0xFF is received
            output.write(b == 0xFF ? input.read() : b);
        }
    }
    /**
     * Sends a command, argument, and input.
     * @param code command code
     * @param path name, or path to resource
     * @param input xml input
     * @throws IOException I/O exception
     */
    private void send(final int code, final String path, final InputStream input) throws IOException {
        out.write(code);
        send(path);
        send(input);
    }
    /**
     * Sends an input stream to the server.
     * @param input xml input
     * @throws IOException I/O exception
     */
    private void send(final InputStream input) throws IOException {
        final BufferedInputStream bis = new BufferedInputStream(input);
        final BufferedOutputStream bos = new BufferedOutputStream(out);
        for(int b; (b = bis.read()) != -1;) {
            // 0x00 and 0xFF will be prefixed by 0xFF
            if(b == 0x00 || b == 0xFF) bos.write(0xFF);
            bos.write(b);
        }
        bos.write(0);
        bos.flush();
        info = receive();
        if(!ok()) throw new IOException(info);
    }
    /**
     * Returns an MD5 hash.
     * @param pw String
     * @return String
     */
    private static String md5(final String pw) {
        final StringBuilder sb = new StringBuilder();
        try {
            final MessageDigest md = MessageDigest.getInstance("MD5");
            md.update(pw.getBytes());
            for(final byte b : md.digest()) {
                final String s = Integer.toHexString(b & 0xFF);
                if(s.length() == 1) sb.append('0');
                sb.append(s);
            }
        } catch(final NoSuchAlgorithmException ex) {
            // should not occur
            ex.printStackTrace();
        }
        return sb.toString();
    }
    /**
     * Inner class for iterative query execution.
     */
    public class Query implements Closeable {
        /** Query id. */
        private final String id;
        /** Cached results. */
        private ArrayList<byte[]> cache;
        /** Cache pointer. */
        private int pos;
        /**
         * Standard constructor.
         * @param query query string
         * @throws IOException I/O exception
         */
        Query(final String query) throws IOException {
            id = exec(0, query);
        }
        /**
         * Binds a value to an external variable.
         * @param name name of variable
         * @param value value
         * @throws IOException I/O exception
         */
        public void bind(final String name, final String value) throws IOException {
            bind(name, value, "");
        }
        /**
         * Binds a value with the specified type to an external variable.
         * @param name name of variable
         * @param value value
         * @param type type (can be an empty string)
         * @throws IOException I/O exception
         */
        public void bind(final String name, final String value, final String type) throws IOException {
            cache = null;
            exec(3, id + '\0' + name + '\0' + value + '\0' + type);
        }
        /**
         * Binds a value to the context item.
         * @param value value
         * @throws IOException I/O exception
         */
        public void context(final String value) throws IOException {
            context(value, "");
        }
        /**
         * Binds a value with the specified type to the context item.
         * @param value value
         * @param type type (can be an empty string)
         * @throws IOException I/O exception
         */
        public void context(final String value, final String type) throws IOException {
            cache = null;
            exec(14, id + '\0' + value + '\0' + type);
        }
        /**
         * Checks for the next item.
         * @return result of check
         * @throws IOException I/O exception
         */
        public boolean more() throws IOException {
            if(cache == null) {
                out.write(4);
                send(id);
                cache = new ArrayList<>();
                final ByteArrayOutputStream os = new ByteArrayOutputStream();
                while(in.read() > 0) {
                    receive(in, os);
                    cache.add(os.toByteArray());
                    os.reset();
                }
                if(!ok()) throw new IOException(receive());
                pos = 0;
            }
            if(pos < cache.size()) return true;
            cache = null;
            return false;
        }
        /**
         * Returns the next item.
         * @return item string
         * @throws IOException I/O Exception
         */
        public String next() throws IOException {
            return more() ? new String(cache.set(pos++, null), UTF8) : null;
        }
        /**
         * Returns the whole result of the query.
         * @return query result
         * @throws IOException I/O Exception
         */
        public String execute() throws IOException {
            return exec(5, id);
        }
        /**
         * Returns query info in a string.
         * @return query info
         * @throws IOException I/O exception
         */
        public String info() throws IOException {
            return exec(6, id);
        }
        /**
         * Returns serialization parameters in a string.
         * @return query info
         * @throws IOException I/O exception
         */
        public String options() throws IOException {
            return exec(7, id);
        }
        /**
         * Closes the query.
         * @throws IOException I/O exception
         */
        @Override
        public void close() throws IOException {
            exec(2, id);
        }
        /**
         * Executes the specified command.
         * @param code command code
         * @param arg argument
         * @return resulting string
         * @throws IOException I/O exception
         */
        private String exec(final int code, final String arg) throws IOException {
            out.write(code);
            send(arg);
            final String s = receive();
            if(!ok()) throw new IOException(receive());
            return s;
        }
    }
}

package com.linghu.util;
import java.io.IOException;
import java.io.OutputStream;
/**
 * This example shows how commands can be executed on a server.
 *
 * This example requires a running database server instance.
 * Documentation: https://docs.basex.org/wiki/Clients
 *
 * @author BaseX Team 2005-22, BSD License
 */
public final class Example {
    /**
     * Main method.
     * @param args command-line arguments
     * @throws IOException I/O exception
     */
    public static void main(final String... args) throws IOException {
        // create session
        try(BaseXClient session = new BaseXClient("localhost", 1984, "admin", "admin")) {
        
            session.query("db:create('Zhang')").execute();
        }
    }
}