Hibernate註解開發

1． PO（簡單）類註解配置

    在hibernate中咱們使用註解，能夠幫助咱們簡化hbm文件配置。

    導入的包是javax.persisitance 

    

    @Entity                //定義一個實體

    @Table                //來描述類與表對應

    @Id                      //來聲明一個主鍵

    @JoinCoulumn(name = "外鍵") //用於指定外鍵類（在外鍵所在的類中配置）

    @JoinTable來描述中間表，並在中間表中描述外鍵分別與兩個多表的映射關係

    @GenerateValue  //用它來聲明一個主鍵生成策略

        默認狀況下至關於native

    能夠選擇的主鍵生成策略 AUTO IDENTITY SEQUENCE

    @Column         //來定義列

    注意：對於PO類中全部屬性，若是你不寫註解，默認狀況下也會在表中生成對應的列。

    列的名稱就是屬性的名稱

    @Temporal來聲明日期類型

        能夠選擇

        TemporalType.DATA   只有年月日  

        TemporalType.TIME   只有小時分鐘秒

        TemporalType.TIMESTAMP 有年月日小時分鐘秒

        咱們最終須要在hibernate.cfg.xml文件中將咱們類中的註解配置引用生效

package com.itheima.domain;

import java.util.Date;

import javax.persistence.Column;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.GenerationType;

import javax.persistence.Id;

import javax.persistence.Table;

import javax.persistence.Temporal;

import javax.persistence.TemporalType;

@Entity   //聲明一個實體

//描述與表對應

@Table(name = "t_book",catalog = "hibernateTest")

public class Book {

    @Id   //主鍵

    //聲明主鍵生成策略，不寫默認是native

    @GeneratedValue(strategy=GenerationType.IDENTITY)  //identity

    private Integer id;

    

    //聲明列。name 對應數據庫的列名，length 長度,nullable 是否爲空

    @Column(name = "name",length=30,nullable =  true)

    private String name;

    

    //聲明時間類型

    @Temporal(TemporalType.TIMESTAMP) //既有日期又有時分秒

    private Date publicactionDate;

 

    private Double price; //由於聲明瞭@Entity 實體，因此這裏價格就算不加註解們也會生成進表中，值都爲默認值

    

    public Double getPrice() {

         return price;

    }

    public void setPrice(Double price) {

         this.price = price;

    }

    public Integer getId() {

         return id;

    }

    public void setId(Integer id) {

         this.id = id;

    }

    public String getName() {

         return name;

    }

    public void setName(String name) {

         this.name = name;

    }

    public Date getPublicactionDate() {

         return publicactionDate;

    }

    public void setPublicactionDate(Date  publicactionDate) {

         this.publicactionDate = publicactionDate;

    }

}

 

 

在實體類中使用註解聲明後，還須要在hibernate.cfg.xml底下配置

<mapping class = "實體類的全類名">

編寫測試類進行保存測試

import java.util.Date;

import org.hibernate.Session;

import org.hibernate.Transaction;

import org.junit.Test;

import com.itheima.domain.Book;

import com.itheima.utils.HibernateUtils;

public class HibernateAnnotionTest {

    @Test

    public void test1(){

         Session session =  HibernateUtils.openSession();

         Transaction transaction =  session.beginTransaction();

         

         Book book = new Book();

         book.setName("一言不合學java");

         book.setPrice(998d);

         book.setPublicactionDate(new Date());

         

         session.save(book);

         

         

         transaction.commit();

         session.close();

         

         

    }

}

 

問題:1.若是咱們主鍵生成策略想使用UUID類型？

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

import javax.persistence.Table;

import javax.persistence.Transient;

import org.hibernate.annotations.GenericGenerator;

@Entity

@Table(catalog = "hibernateTest")

public class Person {

    

    //問題一：問題:1.若是咱們主鍵生成策略想使用UUID類型？

    @Id

    //主鍵成策略擴展的標籤

    @GenericGenerator(name =  "myuuid",strategy="uuid")

    @GeneratedValue(generator="myuuid")

    private String id ;

    

    //問題二：問題2:若是設定類的屬性不在表中映射？

    //使用@Transient

    @Transient

    private String msg;

}

 

對於咱們以上講解的關於屬性配置的註解，咱們也能夠在其對應的getXxx方法去使用

 

 

一對多(多對一)

@OneToMany

@ManyToOne

以Customer與Order爲例

 

Customer類

 

import java.util.HashSet;

import java.util.LinkedHashSet;

import java.util.Set;

 

import javax.persistence.Entity;

import javax.persistence.Id;

import javax.persistence.OneToMany;

import javax.persistence.Table;

 

//客戶的實體類  ------- 一的一方

@Entity

@Table(name = "t_customer",catalog = "hibernateTest")

public class Customer {

    @Id

    private Integer id ; //主鍵

    

    private String name ; //姓名

    

    // 描述客戶能夠有多個訂單

        /*

         * targetEntity至關於<one-to-many class="">

         * mappedBy至關於inverse=true

         */

    @OneToMany(targetEntity=Customer.class,mappedBy="c",orphanRemoval=true)

    //描述客戶能夠有多個訂單

    private Set<Order> order =  new HashSet<Order>();

 

    public Integer getId() {

        return id;

    }

 

    public void setId(Integer id) {

        this.id = id;

    }

 

    public String getName() {

        return name;

    }

 

    public void setName(String name) {

        this.name = name;

    }

 

    public Set<Order> getOrder() {

        return order;

    }

 

    public void setOrder(Set<Order> order) {

        this.order = order;

    }

    

    

}

 

 

Order類

 

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.GenerationType;

import javax.persistence.Id;

import javax.persistence.JoinColumn;

import javax.persistence.ManyToOne;

import javax.persistence.Table;

 

//訂單-----多的一方

@Entity

@Table(name = "t_order")

public class Order {

 

    @Id

    @GeneratedValue(strategy = GenerationType.IDENTITY)

    private Integer id;

 

    private Double money;

 

    private String receiverInfo; // 收貨地址

    // 訂單與客戶關聯

    @ManyToOne(targetEntity = Customer.class)

    @JoinColumn(name = "c_id") // 指定外鍵列

    private Customer c; // 描述訂單屬於某一個客戶

 

    public Customer getC() {

        return c;

    }

 

    public void setC(Customer c) {

        this.c = c;

    }

 

    public Integer getId() {

        return id;

    }

 

    public void setId(Integer id) {

        this.id = id;

    }

 

    public Double getMoney() {

        return money;

    }

 

    public void setMoney(Double money) {

        this.money = money;

    }

 

    public String getReceiverInfo() {

        return receiverInfo;

    }

 

    public void setReceiverInfo(String receiverInfo) {

        this.receiverInfo = receiverInfo;

    }

 

}

 

 

 

示例:保存客戶時，保存訂單

對於這個示例咱們須要在Customer中配置（級聯）cascade操做，<save-update>

 

 

第一種方式，可使用JPA提供的註解

(推薦使用)第二種方式:可使用hibernate提供的註解

    @OneToMany(targetEntity=Customer.class,mappedBy="c")

    @Cascade(CascadeType.SAVE_UPDATE)

    //描述客戶能夠有多個訂單

    private Set<Order> order =  new  HashSet<Order>();

 

如下是示例代碼

將id設爲自動增加

@Test

    //測試級聯保客戶時候自動保存訂單

    public void test2(){

         Session session =  HibernateUtils.openSession();

         Transaction transaction =  session.beginTransaction();

         //訂單1

         Order order1 = new Order();

         order1.setReceiverInfo("福建");

         order1.setMoney(998d);

         //訂單2

         Order order2 = new Order();

         order2.setReceiverInfo("福建");

         order2.setMoney(100d);

         

         //顧客1

         Customer customer = new Customer();

         customer.setName("雷老虎");

         //創建關係

         order1.setC(customer);

         order2.setC(customer);

         

         customer.getOrder().add(order1);

         customer.getOrder().add(order2);

         

         session.save(customer);

         

         transaction.commit();

         session.close();

         

         

    }

 

 

訂單中沒有關聯客戶的id,爲何？

緣由:咱們在Customer中配置了mappedBy= 」 c 」（至關於inverse=true） 它表明的是外鍵的維護由Order方來維護，而Customer不維護，這時你在保存客戶時，級聯保存訂單，是能夠的，可是不能維護外鍵，因此，咱們必須在代碼中添加訂單與客戶關係。

 

擴展:關於hibernate註解@Cascade中的DELETE_ORPHAN過期

s

使用下面方案來替換過期方案

 

      H ibernate關聯映射-多對多

使用註解完成多對多配置.

描述學生與老師.

使用@ManyToMany來配置多對多，只須要在其中一端配置中間表，另外一端使用mappedBy表示放置外鍵維護權。

        建立PO類

T eacher類中

 

import java.util.HashSet;

import java.util.Set;

 

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.GenerationType;

import javax.persistence.Id;

import javax.persistence.ManyToMany;

import javax.persistence.Table;

 

import org.hibernate.annotations.Cascade;

import org.hibernate.annotations.CascadeType;

 

@Entity

@Table(name = "t_teacher")

public class Teacher {

 

    @Id

    @GeneratedValue(strategy = GenerationType.IDENTITY)

    private Integer id;

    private String name;

 

    @ManyToMany(targetEntity = Student.class, mappedBy = "teachers") // 表明由對方來維護外鍵

    @Cascade(CascadeType.ALL)

    private Set<Student> students = new HashSet<Student>();

 

    public Integer getId() {

        return id;

    }

 

    public void setId(Integer id) {

        this.id = id;

    }

 

    public String getName() {

        return name;

    }

 

    public void setName(String name) {

        this.name = name;

    }

 

    public Set<Student> getStudents() {

        return students;

    }

 

    public void setStudents(Set<Student> students) {

        this.students = students;

    }

 

}

 

 

S tudent類中

 

import java.util.HashSet;

import java.util.Set;

 

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.GenerationType;

import javax.persistence.Id;

import javax.persistence.JoinColumn;

import javax.persistence.JoinTable;

import javax.persistence.ManyToMany;

import javax.persistence.Table;

 

import org.hibernate.annotations.Cascade;

import org.hibernate.annotations.CascadeType;

 

@Entity

@Table(name = "t_student")

public class Student {

 

    @Id

    @GeneratedValue(strategy = GenerationType.IDENTITY)

    private Integer id;

 

    private String name;

    @ManyToMany(targetEntity = Teacher.class)

     // 使用JoinTabl來描述中間表，並描述中間表中外鍵與Student,Teacher的映射關係

    // joinColumns它是用來描述(本方)Student與中間表中的映射關係

    // inverseJoinColums它是用來描述對方（Teacher）與中間表中的映射關係

    // 其中referencedColumnName = "id"能夠省略，由於默認就是和主鍵關聯

    @JoinTable(name = "s_t", joinColumns = {

            @JoinColumn(name = "c_student_id", referencedColumnName = "id") }, inverseJoinColumns = {

                    @JoinColumn(name = "c_teacher_id", referencedColumnName = "id") })

    @Cascade(CascadeType.ALL)

    private Set<Teacher> teachers = new HashSet<Teacher>();

 

    public Integer getId() {

        return id;

    }

 

    public void setId(Integer id) {

        this.id = id;

    }

 

    public String getName() {

        return name;

    }

 

    public void setName(String name) {

        this.name = name;

    }

 

    public Set<Teacher> getTeachers() {

        return teachers;

    }

 

    public void setTeachers(Set<Teacher> teachers) {

        this.teachers = teachers;

    }

 

}

總結：

一對多和多對多的配置步驟：

    1.添加關聯關係的註解：@ManyToOne,@OneToMany,ManyToMany

        配置targetEntity(對方的類.class)

    2.哪方維護外鍵：mappedBy="對方中，表示本方的名稱"

    3.在維護關係的一方添加外鍵映射

 

級聯保存操做測試

 由於咱們將外鍵的維護權利由Student來維護，咱們演示保存學生時，將都也級聯保存。

 

 

咱們在Student類中配置了級聯

 

1.  

   級聯刪除操做測試

  H ibernate關聯映射-一對一

    以人與身份證號爲例

 

一對一操做有兩種映射方式:

1. 
   在任意一方添加外鍵
2. 
   主鍵映射

                 外鍵映射

 

         建立實體

User類

上述配置，t_user表放棄對外鍵的維護權利

 

IDCard類

joinColumn指定外鍵列名稱，當前配置外鍵是在t_idcard表中

 

測試代碼

1.  

   主鍵映射

以Husband與Wife爲例

 

W ife的主鍵生成策略是identity

@PrimaryKeyJoinColumn 說明husband與wife是使用主鍵映射

 

H usband的主鍵咱們設置成參考wife的主鍵方式

 

測試操做