hibernate报错Unknown integral data type for ids : java.lang.String

package com.model;

// Generated 2016-10-27 14:02:17 by Hibernate Tools 4.3.1.Final

/**

 * CmDept generated by hbm2java

 */

public class CmDept/* implements java.io.Serializable */{

    private String id;

    private String deptName;

    public CmDept() {

    }

    public CmDept(String id) {

        this.id = id;

    }

    public CmDept(String id, String deptName) {

        this.id = id;

        this.deptName = deptName;

    }

    public String getId() {

        return this.id;

    }

    public void setId(String id) {

        this.id = id;

    }

    public String getDeptName() {

        return this.deptName;

    }

    public void setDeptName(String deptName) {

        this.deptName = deptName;

    }

}

<?xml version="1.0"?>

<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"

"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<!-- Generated 2016-10-27 14:40:22 by Hibernate Tools 3.5.0.Final -->

<hibernate-mapping>

    <class name="com.model.CmDept" table="CM_DEPT">

        <id name="id" type="java.lang.String">

            <column name="ID" />

            <generator class="sequence">

                <param name="sequence">cm_sequence_dept</param>

            </generator>

        </id>

        <property name="deptName" type="java.lang.String">

            <column name="DEPTNAME" />

        </property>

    </class>

</hibernate-mapping>