hibernate中新增记录的问题

Question

问个用hibernate来实现的初级的问题:
我现在有两张表:
stu表
stu_id
stu_name
class_id 是class表的外键

class表
class_id
class_name

class表中有一些班级的数据

我现在想增加一个学生,选择一个班级保存到stu表中.这个stu和class两个表的pojo文件和hbm文件应该怎么写,请大侠写个示例指点一下.

Answer 1

这个就是一对多的关系
[color=red]Stu.hbm.xml[/color]
[code="java"]
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" >

name="Stu"
table="stu"
>
false
name="Id"
type="integer"
column="stu_id"
>

    <property
        name="StuName"
        column="stu_name"
        type="string"
        not-null="false"
        length="20"
    />
    <many-to-one
        name="Class"
        column="class_id"
        class="Myclazz"
        not-null="false"
    >
    </many-to-one>


</class>    

[/code]
Stu类
[code="java"]
package com.haha.base;

import java.io.Serializable;

/**

• This is an object that contains data related to the stu table.
• Do not modify this class because it will be overwritten if the configuration file
• related to this class is modified. *
• @hibernate.class
• table="stu" */

public abstract class BaseStu implements Serializable {

public static String REF = "Stu";
public static String PROP_STU_NAME = "StuName";
public static String PROP_CLASS = "Class";
public static String PROP_ID = "Id";


// constructors
public BaseStu () {
    initialize();
}

/**
 * Constructor for primary key
 */
public BaseStu (java.lang.Integer id) {
    this.setId(id);
    initialize();
}

protected void initialize () {}



private int hashCode = Integer.MIN_VALUE;

// primary key
private java.lang.Integer id;

// fields
private java.lang.String stuName;

// many to one
private com.haha.Myclazz m_class;



/**
 * Return the unique identifier of this class
 * @hibernate.id
 *  generator-class="org.hibernate.id.IdentityGenerator"
 *  column="stu_id"
 */
public java.lang.Integer getId () {
    return id;
}

/**
 * Set the unique identifier of this class
 * @param id the new ID
 */
public void setId (java.lang.Integer id) {
    this.id = id;
    this.hashCode = Integer.MIN_VALUE;
}




/**
 * Return the value associated with the column: stu_name
 */
public java.lang.String getStuName () {
    return stuName;
}

/**
 * Set the value related to the column: stu_name
 * @param stuName the stu_name value
 */
public void setStuName (java.lang.String stuName) {
    this.stuName = stuName;
}



/**
 * Return the value associated with the column: class_id
 */
public com.haha.Myclazz getMyClass () {
    return m_class;
}

/**
 * Set the value related to the column: class_id
 * @param m_class the class_id value
 */
public void setClass (com.haha.Myclazz m_class) {
    this.m_class = m_class;
}




public boolean equals (Object obj) {
    if (null == obj) return false;
    if (!(obj instanceof com.haha.Stu)) return false;
    else {
        com.haha.Stu stu = (com.haha.Stu) obj;
        if (null == this.getId() || null == stu.getId()) return false;
        else return (this.getId().equals(stu.getId()));
    }
}

public int hashCode () {
    if (Integer.MIN_VALUE == this.hashCode) {
        if (null == this.getId()) return super.hashCode();
        else {
            String hashStr = this.getMyClass().getClassName() + ":" + this.getId().hashCode();
            this.hashCode = hashStr.hashCode();
        }
    }
    return this.hashCode;
}


public String toString () {
    return super.toString();
}

}
[/code]

[color=red]Myclazz.hbm.xml/color
[code="java"]
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" >

name="Myclazz"
table="myclazz"
>
false
name="Id"
type="integer"
column="class_id"
>

    <property
        name="ClassName"
        column="class_name"
        type="string"
        not-null="false"
        length="20"
    />


    <set name="Stus" inverse="true">
        <key column="class_id"/>
        <one-to-many class="Stu"/>
    </set>


</class>    

[/code]
MyClazz类
[code="java"]
package com.haha.base;

import java.io.Serializable;

/**

• This is an object that contains data related to the myclazz table.
• Do not modify this class because it will be overwritten if the configuration file
• related to this class is modified. *
• @hibernate.class
• table="myclazz" */

public abstract class BaseMyclazz implements Serializable {

public static String REF = "Myclazz";
public static String PROP_CLASS_NAME = "ClassName";
public static String PROP_ID = "Id";


// constructors
public BaseMyclazz () {
    initialize();
}

/**
 * Constructor for primary key
 */
public BaseMyclazz (java.lang.Integer id) {
    this.setId(id);
    initialize();
}

protected void initialize () {}



private int hashCode = Integer.MIN_VALUE;

// primary key
private java.lang.Integer id;

// fields
private java.lang.String className;

// collections
private java.util.Set<com.haha.Stu> stus;



/**
 * Return the unique identifier of this class
 * @hibernate.id
 *  generator-class="org.hibernate.id.IdentityGenerator"
 *  column="class_id"
 */
public java.lang.Integer getId () {
    return id;
}

/**
 * Set the unique identifier of this class
 * @param id the new ID
 */
public void setId (java.lang.Integer id) {
    this.id = id;
    this.hashCode = Integer.MIN_VALUE;
}




/**
 * Return the value associated with the column: class_name
 */
public java.lang.String getClassName () {
    return className;
}

/**
 * Set the value related to the column: class_name
 * @param className the class_name value
 */
public void setClassName (java.lang.String className) {
    this.className = className;
}



/**
 * Return the value associated with the column: Stus
 */
public java.util.Set<com.haha.Stu> getStus () {
    return stus;
}

/**
 * Set the value related to the column: Stus
 * @param stus the Stus value
 */
public void setStus (java.util.Set<com.haha.Stu> stus) {
    this.stus = stus;
}

public void addToStus (com.haha.Stu stu) {
    if (null == getStus()) setStus(new java.util.TreeSet<com.haha.Stu>());
    getStus().add(stu);
}




public boolean equals (Object obj) {
    if (null == obj) return false;
    if (!(obj instanceof com.haha.Myclazz)) return false;
    else {
        com.haha.Myclazz myclazz = (com.haha.Myclazz) obj;
        if (null == this.getId() || null == myclazz.getId()) return false;
        else return (this.getId().equals(myclazz.getId()));
    }
}

public int hashCode () {
    if (Integer.MIN_VALUE == this.hashCode) {
        if (null == this.getId()) return super.hashCode();
        else {
            String hashStr = this.getClass().getName() + ":" + this.getId().hashCode();
            this.hashCode = hashStr.hashCode();
        }
    }
    return this.hashCode;
}


public String toString () {
    return super.toString();
}

}
[/code]