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Hibernate一對多數據關聯

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。

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。或者在開始為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 2006-08-05 00:44 topquan 閱讀(747) 評論(0) 編輯收藏所屬分類: Hibernate

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Hibernate一對多數據關聯