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Groovy example source code file (GString.java)

This example Groovy source code file (GString.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Groovy tags/keywords

arraylist, charsequence, closure, closure, gstring, gstring, io, ioexception, list, object, object, regex, string, string, stringwriter, util, writable

The Groovy GString.java source code

/*
 * Copyright 2003-2007 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package groovy.lang;

import org.codehaus.groovy.runtime.DefaultGroovyMethods;
import org.codehaus.groovy.runtime.InvokerHelper;

import java.io.IOException;
import java.io.Serializable;
import java.io.StringWriter;
import java.io.Writer;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.regex.Pattern;

/**
 * Represents a String which contains embedded values such as "hello there
 * ${user} how are you?" which can be evaluated lazily. Advanced users can
 * iterate over the text and values to perform special processing, such as for
 * performing SQL operations, the values can be substituted for ? and the
 * actual value objects can be bound to a JDBC statement. The lovely name of
 * this class was suggested by Jules Gosnell and was such a good idea, I
 * couldn't resist :)
 *
 * @author <a href="mailto:james@coredevelopers.net">James Strachan
 * @version $Revision: 21240 $
 */
public abstract class GString extends GroovyObjectSupport implements Comparable, CharSequence, Writable, Buildable, Serializable {

    static final long serialVersionUID = -2638020355892246323L;

    /**
     * A GString containing a single empty String and no values.
     */
    public static final GString EMPTY = new GString(new Object[0]) {
        public String[] getStrings() {
            return new String[]{""};
        }
    };

    private Object[] values;

    public GString(Object values) {
        this.values = (Object[]) values;
    }

    public GString(Object[] values) {
        this.values = values;
    }

    // will be static in an instance

    public abstract String[] getStrings();

    /**
     * Overloaded to implement duck typing for Strings
     * so that any method that can't be evaluated on this
     * object will be forwarded to the toString() object instead.
     */
    public Object invokeMethod(String name, Object args) {
        try {
            return super.invokeMethod(name, args);
        }
        catch (MissingMethodException e) {
            // lets try invoke the method on the real String
            return InvokerHelper.invokeMethod(toString(), name, args);
        }
    }

    public Object[] getValues() {
        return values;
    }

    public GString plus(GString that) {
        List<String> stringList = new ArrayList();
        List<Object> valueList = new ArrayList();

        stringList.addAll(Arrays.asList(getStrings()));
        valueList.addAll(Arrays.asList(getValues()));

        List<String> thatStrings = Arrays.asList(that.getStrings());
        if (stringList.size() > valueList.size()) {
            thatStrings = new ArrayList<String>(thatStrings);
            // merge onto end of previous GString to avoid an empty bridging value
            String s = stringList.get(stringList.size() - 1);
            s += thatStrings.get(0);
            thatStrings.remove(0);
            stringList.set(stringList.size() - 1, s);
        }

        stringList.addAll(thatStrings);
        valueList.addAll(Arrays.asList(that.getValues()));

        final String[] newStrings = new String[stringList.size()];
        stringList.toArray(newStrings);
        Object[] newValues = valueList.toArray();

        return new GString(newValues) {
            public String[] getStrings() {
                return newStrings;
            }
        };
    }

    public GString plus(String that) {
        String[] currentStrings = getStrings();
        String[] newStrings;
        Object[] newValues;

        boolean appendToLastString = currentStrings.length > getValues().length;

        if (appendToLastString) {
            newStrings = new String[currentStrings.length];
        } else {
            newStrings = new String[currentStrings.length + 1];
        }
        newValues = new Object[getValues().length];
        int lastIndex = currentStrings.length;
        System.arraycopy(currentStrings, 0, newStrings, 0, lastIndex);
        System.arraycopy(getValues(), 0, newValues, 0, getValues().length);
        if (appendToLastString) {
            newStrings[lastIndex - 1] += that;
        } else {
            newStrings[lastIndex] = that;
        }

        final String[] finalStrings = newStrings;
        return new GString(newValues) {

            public String[] getStrings() {
                return finalStrings;
            }
        };
    }

    public int getValueCount() {
        return values.length;
    }

    public Object getValue(int idx) {
        return values[idx];
    }

    public String toString() {
        StringWriter buffer = new StringWriter();
        try {
            writeTo(buffer);
        }
        catch (IOException e) {
            throw new StringWriterIOException(e);
        }
        return buffer.toString();
    }

    public Writer writeTo(Writer out) throws IOException {
        String[] s = getStrings();
        int numberOfValues = values.length;
        for (int i = 0, size = s.length; i < size; i++) {
            out.write(s[i]);
            if (i < numberOfValues) {
                final Object value = values[i];

                if (value instanceof Closure) {
                    final Closure c = (Closure) value;

                    if (c.getMaximumNumberOfParameters() == 0) {
                        InvokerHelper.write(out, c.call());
                    } else if (c.getMaximumNumberOfParameters() == 1) {
                        c.call(out);
                    } else {
                        throw new GroovyRuntimeException("Trying to evaluate a GString containing a Closure taking "
                                + c.getMaximumNumberOfParameters() + " parameters");
                    }
                } else {
                    InvokerHelper.write(out, value);
                }
            }
        }
        return out;
    }

    /* (non-Javadoc)
     * @see groovy.lang.Buildable#build(groovy.lang.GroovyObject)
     */

    public void build(final GroovyObject builder) {
        final String[] s = getStrings();
        final int numberOfValues = values.length;

        for (int i = 0, size = s.length; i < size; i++) {
            builder.getProperty("mkp");
            builder.invokeMethod("yield", new Object[]{s[i]});
            if (i < numberOfValues) {
                builder.getProperty("mkp");
                builder.invokeMethod("yield", new Object[]{values[i]});
            }
        }
    }

    public boolean equals(Object that) {
        if (that instanceof GString) {
            return equals((GString) that);
        }
        return false;
    }

    public boolean equals(GString that) {
        return toString().equals(that.toString());
    }

    public int hashCode() {
        return 37 + toString().hashCode();
    }

    public int compareTo(Object that) {
        return toString().compareTo(that.toString());
    }

    public char charAt(int index) {
        return toString().charAt(index);
    }

    public int length() {
        return toString().length();
    }

    public CharSequence subSequence(int start, int end) {
        return toString().subSequence(start, end);
    }

    /**
     * Turns a String into a regular expression pattern
     *
     * @return the regular expression pattern
     */
    public Pattern negate() {
        return DefaultGroovyMethods.bitwiseNegate(toString());
    }
}

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