@Column(length=1000000)
@Lob
private String notes;

<property name="hibernate.hbm2ddl.auto" value="update" />

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Lob;
import javax.persistence.NamedQuery;
import javax.persistence.Table;

@Entity
@Table( name = "usr" )

public class User {
  @Id
  @GeneratedValue
  private Long id;

  @Column( length = 40, unique = true )
  private String name;

  @Lob
  @Column( length = 100000 )
  private String text;

  public long getId() {
    return id;
  }

  public void setName( String name ) {
    this.name = name;
  }

  public String getName() {
    return name;
  }

  public String getText() {
    return text;
  }

  public void setText( String text ) {
    this.text = text;
  }

}

<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="jpatest" transaction-type="RESOURCE_LOCAL">
        <properties>
            <property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5InnoDBDialect"/>
            <property name="hibernate.hbm2ddl.auto" value="update"/>
            <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver"/>
            <property name="hibernate.connection.username" value="root"/>
            <property name="hibernate.connection.password" value="root"/>
            <property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/jpadatabase"/>
            <property name="hibernate.show-sql" value="true"/>
        </properties>
    </persistence-unit>
</persistence>

.....

  @Column( length = 255 )
  private String text;
......

DEBUG SchemaExport:415 - drop table if exists usr
DEBUG SchemaExport:415 - create table usr (id bigint not null auto_increment, name varchar(40) unique, text varchar(255), primary key (id)) ENGINE=InnoDB
INFO SchemaExport:281 - schema export complete

.....
@Lob
@Column( length = 100000 )
private String text;
.......

DEBUG SchemaExport:415 - drop table if exists usr
DEBUG SchemaExport:415 - create table usr (id bigint not null auto_increment, name varchar(40) unique, text longtext, primary key (id)) ENGINE=InnoDB
INFO SchemaExport:281 - schema export complete

INFO TableMetadata:65 - table found: jpadatabase.usr
 INFO TableMetadata:66 - columns: [id, text, name]
 INFO TableMetadata:68 - foreign keys: []
 INFO TableMetadata:69 - indexes: [name, primary]
 DEBUG DefaultIdentifierGeneratorFactory:90 - Setting dialect  [org.hibernate.dialect.MySQL5InnoDBDialect]
 INFO SchemaUpdate:217 - schema update complete

DEBUG SchemaUpdate:203 - alter table usr add column location varchar(255)
INFO SchemaUpdate:217 - schema update complete

ALTER TABLE piece_aud MODIFY notes LONGTEXT;

ALTER TABLE piece_aud MODIFY notes LONGTEXT;

<property name="hibernate.ejb.naming_strategy" value="org.hibernate.cfg.ImprovedNamingStrategy"/>

alter table your_table modify column your_column text

@Type(type="org.hibernate.type.StringClobType")
String message;

@Column(name="your_column_name",columnDefinition="LONGTEXT")
private String notes;