├── build.gradle
└── src
└── main
    ├── java
    │   └── com
    │       └── test
    │           ├── domain
    │           │   └── Person.java
    │           └── web
    │               └── EventManagerServlet.java
    └── webapp
        ├── META-INF
        │   └── web.xml
        └── WEB-INF
            └── classes
                └── persistence.xml

apply plugin: 'java'
apply plugin: 'idea'
apply plugin: 'tomcat'
apply plugin: 'war'

sourceCompatibility = 1.5
version = '1.0'

repositories {
    mavenCentral()
}

buildscript {
    repositories {
        jcenter()
    }

    dependencies {
        classpath 'org.gradle.api.plugins:gradle-tomcat-plugin:1.2.3'
    }
}

dependencies {
    compile 'javax.servlet:javax.servlet-api:3.0.1'
    compile group: 'org.hibernate', name: 'hibernate-core', version: '4.3.5.Final'
    compile group: 'mysql', name: 'mysql-connector-java', version: '5.1.13'

    def tomcatVersion = '7.0.11'
    tomcat "org.apache.tomcat.embed:tomcat-embed-core:${tomcatVersion}",
            "org.apache.tomcat.embed:tomcat-embed-logging-juli:${tomcatVersion}"
    tomcat("org.apache.tomcat.embed:tomcat-embed-jasper:${tomcatVersion}") {
        exclude group: 'org.eclipse.jdt.core.compiler', module: 'ecj'
    }
}

war {
    webXml = file('src/main/webapp/META-INF/web.xml')
}

package com.test.web;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.servlet.ServletException;
import javax.servlet.http.*;
import java.io.IOException;

public class EventManagerServlet extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory("com");
        EntityManager entityManager = entityManagerFactory.createEntityManager();
    }
}

<persistence xmlns="http://java.sun.com/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"
             version="2.0">
    <persistence-unit name="com" transaction-type="RESOURCE_LOCAL">
        <provider>org.hibernate.ejb.HibernatePersistence</provider>
        <class>com.test.domain.Person</class>
        <properties>
            <property name="hibernate.archive.autodetection" value="class, hbm"/>
            <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
            <property name="hibernate.connection.password"></property>
            <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/hibernate</property>
            <property name="hibernate.connection.username">root</property>
            <property name="hibernate.default_schema">hibernate</property>
            <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
            <property name="hibernate.hbm2ddl.auto" value="create"/>

            <property name="hibernate.c3p0.min_size" value="5"/>
            <property name="hibernate.c3p0.max_size" value="20"/>
            <property name="hibernate.c3p0.timeout" value="300"/>
            <property name="hibernate.c3p0.max_statements" value="50"/>
            <property name="hibernate.c3p0.idle_test_period" value="3000"/>
        </properties>
    </persistence-unit>
</persistence>

Servlet.service() for servlet [Event Manager] in context with path [/play] threw exception
javax.persistence.PersistenceException: No Persistence provider for EntityManager named com
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:61)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:39)

├── META-INF
│   ├── MANIFEST.MF
│   └── web.xml
└── WEB-INF
    ├── classes
    │   ├── com
    │   │   └── test
    │   │       ├── domain
    │   │       │   └── Person.class
    │   │       └── web
    │   │           └── EventManagerServlet.class
    │   └── persistence.xml
    ├── lib
    │   ├── antlr-2.7.7.jar
    │   ├── dom4j-1.6.1.jar
    │   ├── hibernate-commons-annotations-4.0.4.Final.jar
    │   ├── hibernate-core-4.3.5.Final.jar
    │   ├── hibernate-jpa-2.1-api-1.0.0.Final.jar
    │   ├── jandex-1.1.0.Final.jar
    │   ├── javassist-3.18.1-GA.jar
    │   ├── javax.servlet-api-3.0.1.jar
    │   ├── jboss-logging-3.1.3.GA.jar
    │   ├── jboss-logging-annotations-1.2.0.Beta1.jar
    │   ├── jboss-transaction-api_1.2_spec-1.0.0.Final.jar
    │   ├── mysql-connector-java-5.1.13.jar
    │   └── xml-apis-1.0.b2.jar
    └── web.xml

classpath 'org.hibernate:hibernate-entitymanager:4.1.7.Final'

sourceSets.all {
    output.resourcesDir = output.classesDir
}