Commons Attributes example source code file (AttributeExpressionParser.java)

This example Commons Attributes source code file (AttributeExpressionParser.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 - Commons Attributes tags/keywords

argument, argument, arraylist, attributeexpressionparser, buildexception, illegal, list, object, parseresult, parseresult, string, string, stringbuffer, stringbuffer, util

The Commons Attributes AttributeExpressionParser.java source code

/*
 * Copyright 2003-2004 The Apache Software Foundation
 * 
 * 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 org.apache.commons.attributes.compiler;

import java.util.ArrayList;
import java.util.List;

import org.apache.tools.ant.BuildException;

/**
 * Parser for attribute expressions.
 */
public class AttributeExpressionParser {
    
    public static class Argument {
        public final String field;
        public final String text;
        public final int length;
        
        public Argument (String field, String text, int length) {
            this.field = field;
            this.text = text;
            this.length = length;
        }
        
        public boolean equalsOrNull (String a, String b) {
            if (a == null) {
                return b == null;
            } else {
                return b != null && a.equals (b);
            }
        }
        
        public boolean equals (Object o) {
            return o instanceof Argument &&
                equalsOrNull (field, ((Argument) o).field) &&
                ((Argument) o).text.equals (text);
        }
        
        public String toString () {
            return "[Argument: " + field + ", " + text + ", " + length + "]";
        }
    }
    
    public static class ParseResult {
        public final List arguments = new ArrayList ();
        public final String className;
        
        public ParseResult (String className) {
            this.className = className;
        }
        
        public boolean equals (Object o) {
            return o instanceof ParseResult &&
                className.equals (((ParseResult) o).className) &&
                arguments.equals (((ParseResult) o).arguments);
        }
        
        public String toString () {
            return "[ParseResult: " + className + ", " + arguments + "]";
        }
    }
    
    protected static Argument nextArgument (String string, int startPos, String filename, int line) {
        if (string.charAt (startPos) == ')') {
            return null;
        }
        
        StringBuffer sb = new StringBuffer ();
        
        int i = startPos;
        int depth = 0;
        while (!( (string.charAt (i) == ',' || string.charAt (i) == ')') && depth == 0)) {
            switch (string.charAt (i)) {
            case '[':
            case '{':
            case '(': depth++; break;
                
            case ']':
            case '}':
            case ')': depth--; break;
                
            case '\'':
            case '"': {
                    // handle string literals
                    char endChar = string.charAt (i);
                    sb.append (string.charAt (i));
                    i++;
                    while (true) {
                        char ch = string.charAt (i);
                        if (ch == '\\') {
                            sb.append (ch);
                            i++;
                            ch = string.charAt (i);
                            sb.append (ch);
                        } else {
                            if (ch == endChar) {
                                break;
                            }
                            sb.append (ch);                            
                        }
                        i++;
                    }
                }
            }
            
            sb.append (string.charAt (i));
            i++;
            if (i == string.length ()) {
                throw new BuildException (filename + ":" + line + ": Unterminated argument: " + string);
            }
        }        
        
        if (string.charAt (i) == ',') {
            i++;
        }
        
        String text = sb.toString ();
        String field = null;
        int eqPos = text.indexOf ('=');
        if (eqPos > -1) {
            boolean identifier = true;
            for (int j = 0; j < eqPos; j++) {
                char ch = text.charAt (j);
                
                if (Character.isJavaIdentifierPart (ch) || ch == ' ') {
                } else {
                    identifier = false;
                }
            }
            
            if (identifier) {
                field = text.substring (0, eqPos).trim ();
                text = text.substring (eqPos + 1).trim ();
            }
        }
        
        Argument arg = new Argument (field, text, i - startPos);
        
        return arg;
    }
    
    public static ParseResult parse (String string, String filename, int line) {
        StringBuffer sb = new StringBuffer ();
        int i = 0;
        while (i < string.length () && (Character.isJavaIdentifierPart (string.charAt (i)) || string.charAt (i) == '.' || string.charAt (i) == ' ')) {
            sb.append (string.charAt (i));
            i++;
        }
        
        if (i == string.length () || string.charAt (i) != '(') {
            throw new BuildException (filename + ":" + line + ": Illegal expression: " + string);
        }
        
        ParseResult result = new ParseResult (sb.toString ());
        
        i++;
        Argument arg = null;
        boolean seenField = false;
        while ((arg = nextArgument (string, i, filename, line)) != null) {
            if (arg.field != null) {
                seenField = true;
            }
            
            if (seenField && arg.field == null) {
                throw new BuildException (filename + ":" + line + ": Un-named parameters must come before the named parameters: " + string);
            }
            
            result.arguments.add (arg);
            i += arg.length;
        }
        
        return result;
    }
}