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	一對多數據關聯

    一.單向一對多數據關聯
    一個用戶有多個地址，在用戶類TUser中包含地址類TAddress集合。

    1.數據模型

    2.表定義sql
    use?sample;

    DROP?TABLE?T_Address;
    DROP?TABLE?T_User;

    CREATE?TABLE?T_User?(
    ???????id?    INT?NOT?NULL?AUTO_INCREMENT
    ?????,?name?    VARCHAR(50)
    ?????,?age?    INT
    ?????,?    PRIMARY?KEY?(id)
    );

    CREATE?TABLE?T_Address?(
    ???????id?    INT?NOT?NULL?AUTO_INCREMENT
    ?????,?address?    VARCHAR(200)
    ?????,?zipcode?    VARCHAR(10)
    ?????,?tel?    VARCHAR(20)
    ?????,?type?    VARCHAR(20)
    ?????,?    user_id?INT?NOT?NULL
    ?????,?idx?    INT
    ?????,?    PRIMARY?KEY?(id)
    ?????,?    INDEX?(user_id)
    ?????,?    CONSTRAINT?FK_T_Address_1?FOREIGN?KEY?(user_id)
    ??????????????????    REFERENCES?T_User?(id)
    );


    3.POJO類
    TUser.java
    package?cn.blogjava.start;

    import?java.util.Set;

    public?class?TUser??implements?java.io.Serializable?{
    ????    //?Fields????
    ?????private?Integer?id;
    ?????    private?Integer?age;
    ?????    private?String?name;
    ?????    private?Set?address;


    ????    //?Constructors

    ????    public?Integer?getAge()?{
    ????????    return?age;
    ????}

    ????    public?void?setAge(Integer?age)?{
    ????????    this.age?=?age;
    ????}


    ????    public?Set?getAddress()?{
    ????????    return?address;
    ????}

    ????    public?void?setAddress(Set?address)?{
    ????????    this.address?=?address;
    ????}

    ????    /**?default?constructor?*/
    ????    public?TUser()?{
    ????}
    ????
    ????    /**?constructor?with?id?*/
    ????    public?TUser(Integer?id)?{
    ????????    this.id?=?id;
    ????}

    ????    //?Property?accessors

    ????    public?Integer?getId()?{
    ????????    return?this.id;
    ????}
    ????
    ????    public?void?setId(Integer?id)?{
    ????????    this.id?=?id;
    ????}

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

    TAddress.java
    package?cn.blogjava.start;

    import?java.io.Serializable;

    public?class?TAddress?implements?Serializable?{
    ????
    ????    private?Integer?id;
    ????    private?String?address;
    ????    private?String?zipcode;
    ????    private?String?tel;
    ????    private?String?type;
    ????    private?Integer?userId;
    ????    private?Integer?idx;
    ????
    ????    public?Integer?getId()?{
    ????????    return?id;
    ????}
    ????    public?void?setId(Integer?id)?{
    ????????    this.id?=?id;
    ????}
    ????    public?String?getAddress()?{
    ????????    return?address;
    ????}
    ????    public?void?setAddress(String?address)?{
    ????????    this.address?=?address;
    ????}
    ????    public?Integer?getIdx()?{
    ????????    return?idx;
    ????}
    ????    public?void?setIdx(Integer?idx)?{
    ????????    this.idx?=?idx;
    ????}
    ????    public?String?getTel()?{
    ????????    return?tel;
    ????}
    ????    public?void?setTel(String?tel)?{
    ????????    this.tel?=?tel;
    ????}
    ????    public?String?getType()?{
    ????????    return?type;
    ????}
    ????    public?void?setType(String?type)?{
    ????????    this.type?=?type;
    ????}
    ????    public?Integer?getUserId()?{
    ????????    return?userId;
    ????}
    ????    public?void?setUserId(Integer?userId)?{
    ????????    this.userId?=?userId;
    ????}
    ????    public?String?getZipcode()?{
    ????????    return?zipcode;
    ????}
    ????    public?void?setZipcode(String?zipcode)?{
    ????????    this.zipcode?=?zipcode;
    ????}

    }

    3.配置文件
    TUser.hbm.xml
    <?xml?version="1.0"?>
    <!DOCTYPE?hibernate-mapping?PUBLIC?"-//Hibernate/Hibernate?Mapping?DTD?3.0//EN"
    "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"    >
    <hibernate-mapping>
    ????    <class?name="cn.blogjava.start.TUser"?table="T_User"?catalog="sample"
    ?????dynamic-update    ="true"?dynamic-insert="true"
    ????    >
    ????????    <id?name="id"?type="integer">
    ????????????    <column?name="id"?/>
    ????????????    <generator?class="native"?/>
    ????????    </id>
    ????????    <property?name="name"?type="string"?column="name"?/>
    ????????    <property?name="age"?type="java.lang.Integer"?column="age"?/>

    ????????    <set?name="address"?table="t_address"?cascade="all"?order-by="zipcode?asc">
    ????????????    <key?column="user_id">
    ????????????    </key>
    ????????????    <one-to-many?class="cn.blogjava.start.TAddress"?/>
    ????????    </set>
    ????    </class>
    </hibernate-mapping>

    TAddress.hbm.xml
    注意：沒有配置user_id字段。
    <?xml?version="1.0"?>
    <!DOCTYPE?hibernate-mapping?PUBLIC?"-//Hibernate/Hibernate?Mapping?DTD?3.0//EN"
    "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"    >
    <hibernate-mapping>
    ????    <class?name="cn.blogjava.start.TAddress"?table="T_Address"?catalog="sample">
    ????????    <id?name="id"?type="integer">
    ????????????    <column?name="id"?/>
    ????????????    <generator?class="native"?/>
    ????????    </id>
    ????????    <property?name="address"?type="string"?column="address"?/>
    ????????    <property?name="zipcode"?type="string"?column="zipcode"?/>
    ????????    <property?name="tel"?type="string"?column="tel"?/>
    ????????    <property?name="type"?type="string"?column="type"?/>
    ????????    <property?name="idx"?type="java.lang.Integer"?column="idx"?/>
    ????    </class>
    </hibernate-mapping>
    4.測試代碼
    package?cn.blogjava.start;

    import?java.util.HashSet;
    import?java.util.Iterator;
    import?java.util.List;

    import?junit.framework.Assert;
    import?junit.framework.TestCase;

    import?org.hibernate.HibernateException;
    import?org.hibernate.Session;
    import?org.hibernate.SessionFactory;
    import?org.hibernate.Transaction;
    import?org.hibernate.cfg.Configuration;


    public?class?HibernateTest?extends?TestCase?{
    ????
    ????Session?session?    =?null;

    ????    protected?void?setUp()?{
    ????????    try?{
    ????????????Configuration?config?    =?new?Configuration().configure();
    ????????????SessionFactory?sessionFactory?    =?config.buildSessionFactory();
    ????????????session?    =?sessionFactory.openSession();
    ????????????
    ????????}?    catch?(HibernateException?e)?{
    ????????????e.printStackTrace();
    ????????}????????
    ????}

    ????    protected?void?tearDown()?{
    ????????    try?{
    ????????????session.close();????????
    ????????}?    catch?(HibernateException?e)?{
    ????????????e.printStackTrace();
    ????????}????????
    ????}????
    ????
    ????    /**
    ?????*?對象持久化測試(Insert方法)
    ?????    */????????
    ????    public?void?testInsert()?{
    ????????Transaction?tran?    =?null;
    ????????    try?{
    ????????
    ????????????TUser?user?    =?new?TUser();
    ????????????user.setName(    "byf");
    ????????????user.setAge(    new?Integer(26));
    ????????????
    ????????????TAddress?addr?    =?new?TAddress();
    ????????????addr.setTel(    "1123");
    ????????????addr.setZipcode(    "233123");
    ????????????addr.setAddress(    "HongKong");
    ????????????
    ????????????TAddress?addr2?    =?new?TAddress();
    ????????????addr2.setTel(    "139");
    ????????????addr2.setZipcode(    "116001");
    ????????????addr2.setAddress(    "dalian");????????????

    ????????????TAddress?addr3?    =?new?TAddress();
    ????????????addr3.setTel(    "136");
    ????????????addr3.setZipcode(    "100080");
    ????????????addr3.setAddress(    "beijing");
    ????????????
    ????????????    //設置關聯
    ????????????HashSet?set?=?new?HashSet();
    ????????????set.add(addr);
    ????????????set.add(addr2);
    ????????????set.add(addr3);
    ????????????user.setAddress(set);
    ???????????????????????????????????
    ????????????tran?    =?session.beginTransaction();????????????????????????????????
    ????????????    //插入user信息
    ????????????session.save(user);
    ????????????session.flush();
    ????????????tran.commit();
    ????????????Assert.assertEquals(user.getId().intValue()    >0?,true);
    ????????}?    catch?(HibernateException?e)?{
    ????????????e.printStackTrace();
    ????????????Assert.fail(e.getMessage());
    ????????????    if(tran?!=?null)?{
    ????????????????    try?{
    ????????????????????tran.rollback();
    ????????????????}?    catch?(Exception?e1)?{
    ????????????????????e1.printStackTrace();
    ????????????????}
    ????????????}
    ????????}
    ????}
    ????
    ????    /**
    ?????*?對象讀取測試(Select方法)
    ?????    */????????????
    ????    public?void?testSelect(){
    ????????String?hql?    =?"?from?TUser?where?name='byf'";
    ????????    try?{
    ????????????List?userList?    =?session.createQuery(hql).list();
    ????????????TUser?user?    =?(TUser)userList.get(0);
    ????????????System.out.println(    "user?name?is?"?+?user.getName());
    ????????????
    ????????????    for?(Iterator?iter?=?user.getAddress().iterator();?iter.hasNext();)?{
    ????????????????TAddress?addr?    =?(TAddress)?iter.next();
    ????????????????System.out.println(    "user?address?is?"?+?addr.getAddress());????????????????
    ????????????}
    ????????????Assert.assertEquals(user.getName(),?    "byf");
    ????????}?    catch?(Exception?e)?{
    ????????????e.printStackTrace();
    ????????????Assert.fail(e.getMessage());
    ????????}
    ????}
    }

    說明:
    一個問題，由于是單向關聯，為了保持關聯關系，我們只能通過主控方對被動方進行級聯更新。如果被關聯方的字段為NOT NULL屬性，當Hibernate創建或者更新關聯關系時，可能出現約束違例。
    例子中T_Address表中的user_id 為NOT NULL，如果在TAddress.hbm.xml映射了全部字段時。創建一個用戶并賦予她地址信息，對于T_Address表而言，hibernate會執行兩條sql語句來保存地址信息。

    要執行兩條SQL語句，是因為關聯是單向的，就是說對于TAddress對象而言，并不知道自己應該與那一個TUser對象關聯，只能先將user_id設為一個空值。
    之后，根據配置文件
    ????????<set?name="address"?table="t_address"?cascade="all"?order-by="zipcode?asc">
    ????????????    <key?column="user_id">
    ????????????    </key>
    ????????????    <one-to-many?class="cn.blogjava.start.TAddress"?/>
    ????????    </set>
    由TUser對象將自身的id賦給addr.user_id，這樣導致addr屬性值變動，在事物提交的時候，會進行update。

    1)當save該用戶的時候，
    insert into t_address? (user_id, address, zipcode, tel) value (null, "HongKong", "233123", "1123")

    2)當tx.commit()時：
    update t_address user_id="1", address="HongKong", zipcode="233123",tel="1123" where id=2;

    這樣，在save user時，就會出現約束違例。

    調整方法：
    可以在定義數據表字段時候，不加NOT NULL約束?；蛘咴陂_始為user_id隨意賦一個非空值(因為還要update，不正確也沒關系)，或者將user_id字段從TAddress.hbm.xml中刪除(本例就是這樣實現)。

    但是這些都是權宜之計，用兩條SQL語句完成一次數據庫操作，性能低下。
    而雙向一對多解決了這個問題。
    下面來實現雙向關聯：
    修改配置文件
    TUser.hbm.xml
    <?xml?version="1.0"?>
    <!DOCTYPE?hibernate-mapping?PUBLIC?"-//Hibernate/Hibernate?Mapping?DTD?3.0//EN"
    "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"    >
    <hibernate-mapping>
    ????    <class?name="cn.blogjava.start.TUser"?table="T_User"?catalog="sample"
    ?????dynamic-update    ="true"?dynamic-insert="true"
    ????    >
    ????????    <id?name="id"?type="integer">
    ????????????    <column?name="id"?/>
    ????????????    <generator?class="native"?/>
    ????????    </id>
    ????????    <property?name="name"?type="string"?column="name"?/>
    ????????    <property?name="age"?type="java.lang.Integer"?column="age"?/>

    ????????    <set?
    ????????????    name="address"?
    ????????????table    ="t_address"?
    ????????????inverse    ="true"
    ????????????cascade    ="all"?
    ????????????order-by    ="zipcode?asc"
    ????????????    >
    ????????????    <key?column="user_id">
    ????????????    </key>
    ????????????    <one-to-many?class="cn.blogjava.start.TAddress"?/>
    ????????    </set>
    ????    </class>
    </hibernate-mapping>

    設定inverse="true",表明將TUser類作為被動類，將數據關聯的維護工作交給關聯對象TAddress來管理。
    在one-to-many模型中，將many一方設為主控方有助于性能的改善。(讓總理記住每個人困難，但是每個人記住總理方便)

    TAddress.hbm.xml
    <?xml?version="1.0"?>
    <!DOCTYPE?hibernate-mapping?PUBLIC?"-//Hibernate/Hibernate?Mapping?DTD?3.0//EN"
    "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"    >
    <hibernate-mapping>
    ????    <class?name="cn.blogjava.start.TAddress"?table="T_Address"?catalog="sample">
    ????????    <id?name="id"?type="integer">
    ????????????    <column?name="id"?/>
    ????????????    <generator?class="native"?/>
    ????????    </id>
    ????????    <property?name="address"?type="string"?column="address"?/>
    ????????    <property?name="zipcode"?type="string"?column="zipcode"?/>
    ????????    <property?name="tel"?type="string"?column="tel"?/>
    ????????    <property?name="type"?type="string"?column="type"?/>
    ????????    <property?name="idx"?type="java.lang.Integer"?column="idx"?/>
    ????????    <many-to-one
    ??????????????????    name="user"?
    ??????????????????class    ="cn.blogjava.start.TUser"
    ??????????????????cascade    ="none"
    ??????????????????outer-join    ="auto"
    ??????????????????update    ="true"??????????????????
    ??????????????????insert    ="true"
    ??????????????????access    ="property"
    ??????????????????column    ="user_id"
    ??????????????????not-null    ="true"
    ????????    />
    ????    </class>
    </hibernate-mapping>

    2.對TAddress.java做如下改造：
    去掉user_id字段，增加user字段，和getter,setter方法。
    package?cn.blogjava.start;

    import?java.io.Serializable;

    public?class?TAddress?implements?Serializable?{
    ????
    ????    private?Integer?id;
    ????    private?String?address;
    ????    private?String?zipcode;
    ????    private?String?tel;
    ????    private?String?type;
    ????    private?Integer?idx;
    ????    private?TUser?user;
    ????
    ????    public?TUser?getUser()?{
    ????????    return?user;
    ????}
    ????    public?void?setUser(TUser?user)?{
    ????????    this.user?=?user;
    ????}
    ????    public?Integer?getId()?{
    ????????    return?id;
    ????}
    ????    public?void?setId(Integer?id)?{
    ????????    this.id?=?id;
    ????}
    ????    public?String?getAddress()?{
    ????????    return?address;
    ????}
    ????    public?void?setAddress(String?address)?{
    ????????    this.address?=?address;
    ????}
    ????    public?Integer?getIdx()?{
    ????????    return?idx;
    ????}
    ????    public?void?setIdx(Integer?idx)?{
    ????????    this.idx?=?idx;
    ????}
    ????    public?String?getTel()?{
    ????????    return?tel;
    ????}
    ????    public?void?setTel(String?tel)?{
    ????????    this.tel?=?tel;
    ????}
    ????    public?String?getType()?{
    ????????    return?type;
    ????}
    ????    public?void?setType(String?type)?{
    ????????    this.type?=?type;
    ????}
    ????    public?String?getZipcode()?{
    ????????    return?zipcode;
    ????}
    ????    public?void?setZipcode(String?zipcode)?{
    ????????    this.zipcode?=?zipcode;
    ????}

    }

    4.測試代碼
    既然TUser不維護關聯關系，需要TAddress需要自己來維護TUser，所以需要addr.setUser(user);
    package?cn.blogjava.start;

    import?java.util.HashSet;
    import?java.util.Iterator;
    import?java.util.List;

    import?junit.framework.Assert;
    import?junit.framework.TestCase;

    import?org.hibernate.HibernateException;
    import?org.hibernate.Session;
    import?org.hibernate.SessionFactory;
    import?org.hibernate.Transaction;
    import?org.hibernate.cfg.Configuration;


    public?class?HibernateTest?extends?TestCase?{
    ????
    ????Session?session?    =?null;

    ????    protected?void?setUp()?{
    ????????    try?{
    ????????????Configuration?config?    =?new?Configuration().configure();
    ????????????SessionFactory?sessionFactory?    =?config.buildSessionFactory();
    ????????????session?    =?sessionFactory.openSession();
    ????????????
    ????????}    ?catch?(HibernateException?e)?{
    ????????????e.printStackTrace();
    ????????}    ????????
    ????}

    ????    protected?void?tearDown()?{
    ????????    try?{
    ????????????session.close();????????
    ????????}    ?catch?(HibernateException?e)?{
    ????????????e.printStackTrace();
    ????????}    ????????
    ????}    ????
    ????
    ????    /**
    ?????*?對象持久化測試(Insert方法)
    ?????    */    ????????
    ????    public?void?testInsert()?{
    ????????Transaction?tran?    =?null;
    ????????    try?{
    ????????
    ????????????TUser?user?    =?new?TUser();
    ????????????user.setName(    "byf");
    ????????????user.setAge(    new?Integer(26));
    ????????????
    ????????????TAddress?addr?    =?new?TAddress();
    ????????????addr.setTel(    "1123");
    ????????????addr.setZipcode(    "233123");
    ????????????addr.setAddress(    "HongKong");
    ????????????addr.setUser(user);
    ????????????
    ????????????TAddress?addr2?    =?new?TAddress();
    ????????????addr2.setTel(    "139");
    ????????????addr2.setZipcode(    "116001");
    ????????????addr2.setAddress(    "dalian");???????
    ????????????addr2.setUser(user);

    ????????????TAddress?addr3?    =?new?TAddress();
    ????????????addr3.setTel(    "136");
    ????????????addr3.setZipcode(    "100080");
    ????????????addr3.setAddress(    "beijing");
    ????????????addr3.setUser(user);
    ????????????
    ????????????    //設置關聯
    ????????????HashSet?set?=?new?HashSet();
    ????????????set.add(addr);
    ????????????set.add(addr2);
    ????????????set.add(addr3);
    ????????????user.setAddress(set);
    ???????????????????????????????????
    ????????????tran?    =?session.beginTransaction();????????????????????????????????
    ????????????    //插入user信息
    ????????????session.save(user);
    ????????????session.flush();
    ????????????tran.commit();
    ????????????Assert.assertEquals(user.getId().intValue()    >0?,true);
    ????????}    ?catch?(HibernateException?e)?{
    ????????????e.printStackTrace();
    ????????????Assert.fail(e.getMessage());
    ????????????    if(tran?!=?null)?{
    ????????????????    try?{
    ????????????????????tran.rollback();
    ????????????????}    ?catch?(Exception?e1)?{
    ????????????????????e1.printStackTrace();
    ????????????????}
    ????????????}
    ????????}
    ????}
    ????
    ????    /**
    ?????*?對象讀取測試(Select方法)
    ?????    */    ????????????
    ????    public?void?testSelect(){
    ????????String?hql?    =?"?from?TUser?where?name='byf'";
    ????????    try?{
    ????????????List?userList?    =?session.createQuery(hql).list();
    ????????????TUser?user?    =?(TUser)userList.get(0);
    ????????????System.out.println(    "user?name?is?"?+?user.getName());
    ????????????
    ????????????    for?(Iterator?iter?=?user.getAddress().iterator();?iter.hasNext();)?{
    ????????????????TAddress?addr?    =?(TAddress)?iter.next();
    ????????????????System.out.println(    "user?address?is?"?+?addr.getAddress());????????????????
    ????????????}
    ????????????Assert.assertEquals(user.getName(),?    "byf");
    ????????}    ?catch?(Exception?e)?{
    ????????????e.printStackTrace();
    ????????????Assert.fail(e.getMessage());
    ????????}
    ????}
    }
    
	
    posted on 2006-07-05 15:13 knowhow 閱讀(556) 評論(1)  編輯  收藏  所屬分類: ORM：Hibernate及其他 
    

    







    
	    
    










    








    

				

    





    







    
        
	



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