AbstractHookDefinition.java

/**
 * ***************************************************************************
 * Copyright (c) 2010 Qcadoo Limited
 * Project: Qcadoo Framework
 * Version: 1.4
 *
 * This file is part of Qcadoo.
 *
 * Qcadoo is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published
 * by the Free Software Foundation; either version 3 of the License,
 * or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty
 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 * ***************************************************************************
 */
package com.qcadoo.model.internal.hooks;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.Arrays;

import org.apache.commons.lang3.StringUtils;
import org.apache.commons.lang3.builder.EqualsBuilder;
import org.apache.commons.lang3.builder.HashCodeBuilder;
import org.springframework.context.ApplicationContext;

/**
 * Abstract superclass which provides some common building-blocks for Java hooks.
 * 
 * @author Marcin Kubala
 * @since 1.4
 */
public abstract class AbstractHookDefinition {
    private final String pluginIdentifier;

    private final String className;

    private final String methodName;

    private final Object bean;

    private final Method method;

    protected AbstractHookDefinition(final String className, final String methodName, final String pluginIdentifier,
            final ApplicationContext applicationContext) throws HookInitializationException {
        this.pluginIdentifier = pluginIdentifier;
        this.className = className;
        this.methodName = methodName;

        Class<?> clazz = getHookClass(className);
        this.bean = getHookBean(clazz, applicationContext);
        this.method = getMethod(clazz, methodName);

        checkHookMethodModifiers();
    }

    protected abstract Class<?>[] getParameterTypes();

    protected Object performCall(final Object... args) {
        try {
            return getMethod().invoke(getBean(), args);
        } catch (IllegalArgumentException e) {
            throw new IllegalStateException("Failed to invoke hook method", e);
        } catch (IllegalAccessException e) {
            throw new IllegalStateException("Failed to invoke hook method", e);
        } catch (InvocationTargetException e) {
            throw new IllegalStateException("Failed to invoke hook method", e);
        }
    }

    public final Method getMethod() {
        return method;
    }

    public final Object getBean() {
        return bean;
    }

    public String getPluginIdentifier() {
        return pluginIdentifier;
    }

    private Class<?> getHookClass(final String hookClassName) throws HookInitializationException {
        if (StringUtils.isBlank(className)) {
            throw new HookInitializationException(className, methodName, "Hook class name cannot be empty");
        }
        try {
            return Thread.currentThread().getContextClassLoader().loadClass(hookClassName);
        } catch (ClassNotFoundException e) {
            throw new HookInitializationException(className, methodName, "Failed to find class '" + hookClassName
                    + "', please make sure that there is no typo", e);
        }
    }

    private Object getHookBean(final Class<?> clazz, final ApplicationContext applicationContext)
            throws HookInitializationException {
        Object hookBean = applicationContext.getBean(clazz);
        if (hookBean == null) {
            throw new HookInitializationException(
                    className,
                    methodName,
                    "Failed to find bean for class '"
                            + clazz.getCanonicalName()
                            + "', please make sure that there is no typo, class have @Service or @Component annotation and its package is registered in the Spring component-scan feature");
        }
        return hookBean;
    }

    private void checkHookMethodModifiers() throws HookInitializationException {
        if (!Modifier.isPublic(method.getModifiers())) {
            throw new HookInitializationException(className, methodName, "Hook method '"
                    + method.getDeclaringClass().getCanonicalName() + "#" + method.getName()
                    + "' has invalid visibility, must be public");
        }
    }

    private Method getMethod(final Class<?> clazz, final String methodName) throws HookInitializationException {
        if (StringUtils.isBlank(methodName)) {
            throw new HookInitializationException(className, methodName, "Hook method name cannot be empty");
        }
        try {
            return clazz.getMethod(methodName, getParameterTypes());
        } catch (SecurityException e) {
            throw new HookInitializationException(className, methodName, "Failed to access hook method '"
                    + clazz.getCanonicalName() + "#" + methodName + "'", e);
        } catch (NoSuchMethodException e) {
            throw new HookInitializationException(className, methodName, "Failed to find hook method '"
                    + clazz.getCanonicalName() + "#" + methodName
                    + "', please make sure that there is no typo and parameters' types are valid ("
                    + Arrays.toString(getParameterTypes()) + ")", e);
        }
    }

    @Override
    public boolean equals(final Object obj) {
        if (obj == null) {
            return false;
        }
        if (obj == this) {
            return true;
        }
        if (obj.getClass() != getClass()) {
            return false;
        }
        AbstractHookDefinition rhs = (AbstractHookDefinition) obj;
        return new EqualsBuilder().append(this.className, rhs.className).append(this.methodName, rhs.methodName)
                .append(this.pluginIdentifier, rhs.pluginIdentifier).isEquals();
    }

    @Override
    public int hashCode() {
        return new HashCodeBuilder().append(className).append(methodName).append(pluginIdentifier).toHashCode();
    }
}