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/*
 * Copyright 2004-2006 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 org.compass.core.util;

import java.util.Collection;
import java.util.Map;

/**
 * Assert utility class that assists in validating arguments. Useful for
 * identifying programmer errors early and obviously at runtime.
 *
 * <p>For example, if the contract of a public method states it does not allow null
 * arguments, Assert can be used to validate that contract. Doing this clearly
 * indicates a contract violation when it occurs and protects the class's
 * invariants.
 *
 * <p>Typically used to validate method arguments rather than configuration
 * properties, to check for cases that are usually programmer errors rather than
 * configuration errors. In contrast to config initialization code, there is
 * usally no point in falling back to defaults in such methods.
 *
 * <p>This class is similar to JUnit's assertion library. If an argument value is
 * deemed invalid, an IllegalArgumentException is thrown. For example:
 *
 * <pre>
 * Assert.notNull(clazz, "The class must not be null");
 * Assert.isTrue(i > 0, "The value must be greater than zero");</pre>
 *
 * Mainly for internal use within the framework; consider Jakarta's Commons Lang
 * >= 2.0 for a more comprehensive suite of assertion utilities.
 *
 * @author kimchy
 */
public abstract class Assert {

    /**
     * Assert a boolean expression, throwing <code>IllegalArgumentException</code>
     * if the test result is <code>false</code>.
     * <pre>
     * Assert.isTrue(i > 0, "The value must be greater than zero");</pre>
     * @param expression a boolean expression
     * @param message the exception message to use if the assertion fails
     * @throws IllegalArgumentException if expression is <code>false</code>
     */
    public static void isTrue(boolean expression, String message) {
        if (!expression) {
            throw new IllegalArgumentException(message);
        }
    }

    /**
     * Assert a boolean expression, throwing <code>IllegalArgumentException</code>
     * if the test result is <code>false</code>.
     * <pre>
     * Assert.isTrue(i > 0);</pre>
     * @param expression a boolean expression
     * @throws IllegalArgumentException if expression is <code>false</code>
     */
    public static void isTrue(boolean expression) {
        isTrue(expression, "[Assertion failed] - this expression must be true");
    }

    /**
     * Assert that an object is not null.
     * <pre>
     * Assert.notNull(clazz, "The class must not be null");</pre>
     * @param object the object to check
     * @param message the exception message to use if the assertion fails
     * @throws IllegalArgumentException if the object is <code>null</code>
     */
    public static void notNull(Object object, String message) {
        if (object == null) {
            throw new IllegalArgumentException(message);
        }
    }

    /**
     * Assert that an object is not null.
     * <pre>
     * Assert.notNull(clazz);</pre>
     * @param object the object to check
     * @throws IllegalArgumentException if the object is <code>null</code>
     */
    public static void notNull(Object object) {
        notNull(object, "[Assertion failed] - this argument is required; it cannot be null");
    }


    /**
     * Assert that a string is not empty; that is, it must not be <code>null</code> and not empty.
     * <pre>
     * Assert.hasLength(name, "Name must not be empty");</pre>
     * @param text the string to check
     * @param message the exception message to use if the assertion fails
     * @see StringUtils#hasLength
     */
    public static void hasLength(String text, String message) {
        if (!StringUtils.hasLength(text)) {
            throw new IllegalArgumentException(message);
        }
    }

    /**
     * Assert that a string is not empty; that is, it must not be <code>null</code> and not empty.
     * <pre>
     * Assert.hasLength(name);</pre>
     * @param text the string to check
     * @see StringUtils#hasLength
     */
    public static void hasLength(String text) {
        hasLength(text, "[Assertion failed] - this String argument must have length; it cannot be <code>null</code> or empty");
    }

    /**
     * Assert that a string has valid text content; that is, it must not be <code>null</code>
     * and must contain at least one non-whitespace character.
     * <pre>
     * Assert.hasText(name, "Name must not be empty");</pre>
     * @param text the string to check
     * @param message the exception message to use if the assertion fails
     * @see StringUtils#hasText
     */
    public static void hasText(String text, String message) {
        if (!StringUtils.hasText(text)) {
            throw new IllegalArgumentException(message);
        }
    }

    /**
     * Assert that a string has valid text content; that is, it must not be <code>null</code>
     * and must contain at least one non-whitespace character.
     * <pre>
     * Assert.hasText(name, "Name must not be empty");</pre>
     * @param text the string to check
     * @see StringUtils#hasText
     */
    public static void hasText(String text) {
        hasText(text,
                "[Assertion failed] - this String argument must have text; it cannot be <code>null</code>, empty, or blank");
    }

    /**
     * Assert that the given text does not contain the given substring.
     * <pre>
     * Assert.doesNotContain(name, "rod", "Name must not contain 'rod'");</pre>
     * @param textToSearch the text to search
     * @param substring the substring to find within the text
     * @param message the exception message to use if the assertion fails
     */
    public static void doesNotContain(String textToSearch, String substring, String message) {
        if (textToSearch.indexOf(substring) != -1) {
            throw new IllegalArgumentException(message);
        }
    }

    /**
     * Assert that the given text does not contain the given substring.
     * <pre>
     * Assert.doesNotContain(name, "rod");</pre>
     * @param textToSearch the text to search
     * @param substring the substring to find within the text
     */
    public static void doesNotContain(String textToSearch, String substring) {
        doesNotContain(textToSearch, substring,
                "[Assertion failed] - this String argument must not contain the substring [" + substring + "]");
    }


    /**
     * Assert that an array has elements; that is, it must not be
     * <code>null</code> and must have at least one element.
     * <pre>
     * Assert.notEmpty(array, "The array must have elements");</pre>
     * @param array the array to check
     * @param message the exception message to use if the assertion fails
     * @throws IllegalArgumentException if the object array is <code>null</code> or has no elements
     */
    public static void notEmpty(Object[] array, String message) {
        if (array == null || array.length == 0) {
            throw new IllegalArgumentException(message);
        }
    }

    /**
     * Assert that an array has elements; that is, it must not be
     * <code>null</code> and must have at least one element.
     * <pre>
     * Assert.notEmpty(array);</pre>
     * @param array the array to check
     * @throws IllegalArgumentException if the object array is <code>null</code> or has no elements
     */
    public static void notEmpty(Object[] array) {
        notEmpty(array, "[Assertion failed] - this array must not be empty: it must contain at least 1 element");
    }

    /**
     * Assert that a collection has elements; that is, it must not be
     * <code>null</code> and must have at least one element.
     * <pre>
     * Assert.notEmpty(collection, "Collection must have elements");</pre>
     * @param collection the collection to check
     * @param message the exception message to use if the assertion fails
     * @throws IllegalArgumentException if the collection is <code>null</code> or has no elements
     */
    public static void notEmpty(Collection collection, String message) {
        if (collection == null || collection.isEmpty()) {
            throw new IllegalArgumentException(message);
        }
    }

    /**
     * Assert that a collection has elements; that is, it must not be
     * <code>null</code> and must have at least one element.
     * <pre>
     * Assert.notEmpty(collection, "Collection must have elements");</pre>
     * @param collection the collection to check
     * @throws IllegalArgumentException if the collection is <code>null</code> or has no elements
     */
    public static void notEmpty(Collection collection) {
        notEmpty(collection,
                "[Assertion failed] - this collection must not be empty: it must contain at least 1 element");
    }

    /**
     * Assert that a Map has entries; that is, it must not be <code>null</code>
     * and must have at least one entry.
     * <pre>
     * Assert.notEmpty(map, "Map must have entries");</pre>
     * @param map the map to check
     * @param message the exception message to use if the assertion fails
     * @throws IllegalArgumentException if the map is <code>null</code> or has no entries
     */
    public static void notEmpty(Map map, String message) {
        if (map == null || map.isEmpty()) {
            throw new IllegalArgumentException(message);
        }
    }

    /**
     * Assert that a Map has entries; that is, it must not be <code>null</code>
     * and must have at least one entry.
     * <pre>
     * Assert.notEmpty(map);</pre>
     * @param map the map to check
     * @throws IllegalArgumentException if the map is <code>null</code> or has no entries
     */
    public static void notEmpty(Map map) {
        notEmpty(map, "[Assertion failed] - this map must not be empty; it must contain at least one entry");
    }


    /**
     * Assert that the provided object is an instance of the provided class.
     * <pre>
     * Assert.instanceOf(Foo.class, foo);</pre>
     * @param clazz the required class
     * @param obj the object to check
     * @throws IllegalArgumentException if the object is not an instance of clazz
     * @see Class#isInstance
     */
    public static void isInstanceOf(Class clazz, Object obj) {
        isInstanceOf(clazz, obj, "");
    }

    /**
     * Assert that the provided object is an instance of the provided class.
     * <pre>
     * Assert.instanceOf(Foo.class, foo);</pre>
     * @param clazz the required class
     * @param obj the object to check
     * @param message a message which will be prepended to the message produced by
     * the function itself, and which may be used to provide context. It should
     * normally end in a ":" or ". " so that the function generate message looks
     * ok when prepended to it.
     * @throws IllegalArgumentException if the object is not an instance of clazz
     * @see Class#isInstance
     */
    public static void isInstanceOf(Class clazz, Object obj, String message) {
        Assert.notNull(clazz, "The clazz to perform the instanceof assertion cannot be null");
        Assert.isTrue(clazz.isInstance(obj), message +
                "Object of class '" + (obj != null ? obj.getClass().getName() : "[null]") +
                "' must be an instance of '" + clazz.getName() + "'");
    }


    /**
     * Assert a boolean expression, throwing <code>IllegalStateException</code>
     * if the test result is <code>false</code>. Call isTrue if you wish to
     * throw IllegalArgumentException on an assertion failure.
     * <pre>
     * Assert.state(id == null, "The id property must not already be initialized");</pre>
     * @param expression a boolean expression
     * @param message the exception message to use if the assertion fails
     * @throws IllegalStateException if expression is <code>false</code>
     */
    public static void state(boolean expression, String message) {
        if (!expression) {
            throw new IllegalStateException(message);
        }
    }

    /**
     * Assert a boolean expression, throwing <code>IllegalStateException</code>
     * if the test result is <code>false</code>. Call isTrue if you wish to
     * throw IllegalArgumentException on an assertion failure.
     * <pre>
     * Assert.state(id == null);</pre>
     * @param expression a boolean expression
     * @throws IllegalStateException if expression is <code>false</code>
     */
    public static void state(boolean expression) {
        state(expression, "[Assertion failed] - this state invariant must be true");
    }

}
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