summaryrefslogtreecommitdiff
path: root/Master/texmf-dist/source/support/arara/src/main/java/com/github/cereda/arara/utils/ClassLoadingUtils.java
blob: c40536ce08f6249836e6c1fb7e9f73a5f3fa5c88 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
/**
 * Arara, the cool TeX automation tool
 * Copyright (c) 2012 -- 2018, Paulo Roberto Massa Cereda 
 * All rights reserved.
 *
 * Redistribution and  use in source  and binary forms, with  or without
 * modification, are  permitted provided  that the  following conditions
 * are met:
 *
 * 1. Redistributions  of source  code must  retain the  above copyright
 * notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form  must reproduce the above copyright
 * notice, this list  of conditions and the following  disclaimer in the
 * documentation and/or other materials provided with the distribution.
 *
 * 3. Neither  the name  of the  project's author nor  the names  of its
 * contributors may be used to  endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS  PROVIDED BY THE COPYRIGHT  HOLDERS AND CONTRIBUTORS
 * "AS IS"  AND ANY  EXPRESS OR IMPLIED  WARRANTIES, INCLUDING,  BUT NOT
 * LIMITED  TO, THE  IMPLIED WARRANTIES  OF MERCHANTABILITY  AND FITNESS
 * FOR  A PARTICULAR  PURPOSE  ARE  DISCLAIMED. IN  NO  EVENT SHALL  THE
 * COPYRIGHT HOLDER OR CONTRIBUTORS BE  LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY,  OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT  NOT LIMITED  TO, PROCUREMENT  OF SUBSTITUTE  GOODS OR  SERVICES;
 * LOSS  OF USE,  DATA, OR  PROFITS; OR  BUSINESS INTERRUPTION)  HOWEVER
 * CAUSED AND  ON ANY THEORY  OF LIABILITY, WHETHER IN  CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
 * WAY  OUT  OF  THE USE  OF  THIS  SOFTWARE,  EVEN  IF ADVISED  OF  THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
package com.github.cereda.arara.utils;

import com.github.cereda.arara.model.Pair;
import java.io.File;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLClassLoader;

/**
 * Implements utilitary methods for classloading and object instantiation.
 * @author Paulo Roberto Massa Cereda
 * @version 4.0
 * @since 4.0
 */
public class ClassLoadingUtils {

    /**
     * Loads a class from the provided file, potentially a Java archive.
     * @param file File containing the Java bytecode (namely, a JAR).
     * @param name The canonical name of the class.
     * @return A pair representing the status and the class.
     */
    public static Pair<Integer, Class> loadClass(File file, String name) {

        // status and class to be returned,
        // it defaults to an object class
        int status = 0;
        Class value = Object.class;

        // if file does not exist, nothing
        // can be done, status is changed
        if (!file.exists()) {
            status = 1;
        } else {
            
            // classloading involves defining
            // a classloader and fetching the
            // desired class from it, based on
            // the provided file archive
            try {
                
                // creates a new classloader with
                // the provided file (potentially
                // a JAR file)
                URLClassLoader classloader = new URLClassLoader(
                        new URL[]{
                            file.toURI().toURL()
                        },
                        ClassLoadingUtils.class.getClassLoader()
                );
                
                // fetches the class from the
                // instantiated classloader
                value = Class.forName(name, true, classloader);
                
            } catch (MalformedURLException nothandled1) {
                
                // the file URL is incorrect,
                // update status accordingly
                status = 2;
                
            } catch (ClassNotFoundException nothandled2) {
                
                // the class was not found,
                // update status accordingly
                status = 3;
                
            }
        }

        // return a new pair based on the
        // current status and class holder
        return new Pair<Integer, Class>(status, value);
    }

    /**
     * Loads a class from the provided file, instantiating it.
     * @param file File containing the Java bytecode (namely, a JAR).
     * @param name The canonical name of the class.
     * @return A pair representing the status and the class object.
     */
    public static Pair<Integer, Object> loadObject(File file, String name) {

        // load the corresponding class
        // based on the qualified name
        Pair<Integer, Class> pair = loadClass(file, name);

        // status and object to be returned,
        // it defaults to an object
        int status = pair.getFirstElement();
        Object value = new Object();

        // checks if the class actually
        // exists, otherwise simply
        // ignore instantiation
        if (status == 0) {
            
            // object instantiation relies
            // on the default constructor
            // (without arguments), class
            // must implement it
            
            // OBS: constructors with arguments
            // must be invoked through reflection
            try {
                
                // get the class reference from
                // the pair and instantiate it
                // by invoking the default
                // constructor (without arguments)
                value = pair.getSecondElement().newInstance();
                
            } catch (IllegalAccessException nothandled1) {
                
                // the object instantiation violated
                // an access policy, status is updated
                status = 4;
                
            } catch (InstantiationException nothandled2) {
                
                // an instantiation exception has
                // occurred, status is updated
                status = 5;
                
            }
        }

        // return a new pair based on the
        // current status and object holder
        return new Pair<Integer, Object>(status, value);
    }

}