MyEclipe+Hibernate增删查改快速入门

最新推荐文章于 2020-08-10 18:42:28 发布

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本文详细介绍如何使用Hibernate进行数据库操作，包括创建映射文件、实体类、CRUD操作等，并通过具体示例展示了插入、删除、查询及更新的具体实现。

一、先给出测试用表的结构和原始数据：

create table T_GRADES
(
  ID        VARCHAR2(20) PRIMARY KEY,
  SUBJECT   VARCHAR2(20),
  GRADE     NUMBER(3,1),
  TEACHER   VARCHAR2(20),
  STUDENTID VARCHAR2(20)
);
INSERT INTO T_GRADES
  (ID, SUBJECT, GRADE, TEACHER, STUDENTID)
VALUES
  ('1', '语文', 80, 'Miss_zhang', '050104010121');
INSERT INTO T_GRADES
  (ID, SUBJECT, GRADE, TEACHER, STUDENTID)
VALUES
  ('2', '数学', 90, 'Miss_zhang', '050104010121');
INSERT INTO T_GRADES
  (ID, SUBJECT, GRADE, TEACHER, STUDENTID)
VALUES
  ('3', '数学', 99.9, 'MR_huang', '050104010120');
INSERT INTO T_GRADES
  (ID, SUBJECT, GRADE, TEACHER, STUDENTID)
VALUES
  ('4', '英语', 90, 'MR_huang', '050104010120');
COMMIT;

二、在Myeclipse中新建一个java project，然后为该project 添加hibernate capabilities，在添加的过程中，会根据你设置的路径生成一些文件，包括：hibernate.cfg.xml，HibernateSessinFactory.java，当然会把需要的jar包一包含进来，下面就是自己的开发工作了。

三、首先给出MyEclipse生成的原始的hibernate.cfg.xml文件：

<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
          "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
          "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<!-- Generated by MyEclipse Hibernate Tools.                   -->
<hibernate-configuration>
	<session-factory>
		<property name="connection.username">scott</property>
		<property name="connection.url">
			jdbc:oracle:thin:@127.0.0.1:1521:orcl
		</property>
		<property name="connection.password">test</property>
		<property name="connection.driver_class">
			oracle.jdbc.driver.OracleDriver
		</property>
	</session-factory>
</hibernate-configuration>

现在这个文件中内容是在我们添加hibernate capabilities时，MyEclipse根据你的设置自动生成的，这部分是不用改动的。将来我们需要做的就是添加
类映射文件了。在<session_factory>中添加<mapping resource=""/>之类的标签。

四、下面给出Myeclipse自动生成的会话工厂类，这个类我们一点都不用动，直接用其中实现的方法即可。

package com.neuqsoft.hibernate;

import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.cfg.Configuration;

/**
 * Configures and provides access to Hibernate sessions, tied to the
 * current thread of execution.  Follows the Thread Local Session
 * pattern, see {@link http://hibernate.org/42.html }.
 */
public class HibernateSessionFactory {

    /** 
     * Location of hibernate.cfg.xml file.
     * Location should be on the classpath as Hibernate uses  
     * #resourceAsStream style lookup for its configuration file. 
     * The default classpath location of the hibernate config file is 
     * in the default package. Use #setConfigFile() to update 
     * the location of the configuration file for the current session.   
     */
    private static String CONFIG_FILE_LOCATION = "/hibernate.cfg.xml";
	private static final ThreadLocal<Session> threadLocal = new ThreadLocal<Session>();
    private  static Configuration configuration = new Configuration();    
    private static org.hibernate.SessionFactory sessionFactory;
    private static String configFile = CONFIG_FILE_LOCATION;

	static {
    	try {
			configuration.configure(configFile);
			sessionFactory = configuration.buildSessionFactory();
		} catch (Exception e) {
			System.err
					.println("%%%% Error Creating SessionFactory %%%%");
			e.printStackTrace();
		}
    }
    private HibernateSessionFactory() {
    }
	
	/**
     * Returns the ThreadLocal Session instance.  Lazy initialize
     * the <code>SessionFactory</code> if needed.
     *
     *  @return Session
     *  @throws HibernateException
     */
    public static Session getSession() throws HibernateException {
        Session session = (Session) threadLocal.get();

		if (session == null || !session.isOpen()) {
			if (sessionFactory == null) {
				rebuildSessionFactory();
			}
			session = (sessionFactory != null) ? sessionFactory.openSession()
					: null;
			threadLocal.set(session);
		}

        return session;
    }

	/**
     *  Rebuild hibernate session factory
     *
     */
	public static void rebuildSessionFactory() {
		try {
			configuration.configure(configFile);
			sessionFactory = configuration.buildSessionFactory();
		} catch (Exception e) {
			System.err
					.println("%%%% Error Creating SessionFactory %%%%");
			e.printStackTrace();
		}
	}

	/**
     *  Close the single hibernate session instance.
     *
     *  @throws HibernateException
     */
    public static void closeSession() throws HibernateException {
        Session session = (Session) threadLocal.get();
        threadLocal.set(null);

        if (session != null) {
            session.close();
        }
    }

	/**
     *  return session factory
     *
     */
	public static org.hibernate.SessionFactory getSessionFactory() {
		return sessionFactory;
	}

	/**
     *  return session factory
     *
     *	session factory will be rebuilded in the next call
     */
	public static void setConfigFile(String configFile) {
		HibernateSessionFactory.configFile = configFile;
		sessionFactory = null;
	}

	/**
     *  return hibernate configuration
     *
     */
	public static Configuration getConfiguration() {
		return configuration;
	}

}

五、下面开始就是自己亲手要做的工作了，下面的顺序依个人喜好而定，在程序运行之前只要这些文件齐全，应该就没有问题。
5.1 给出我写的Java类映射文件。

<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE hibernate-mapping  PUBLIC
          "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
          "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.neuqsoft.model">
	<class name="Grade" table="T_GRADES">
		<id name="id" column="ID">
			<generator class="assigned"></generator>
		</id>
		<property name="subject" column="SUBJECT"></property>
		<property name="grade" column="GRADE"></property>
		<property name="teacher" column="TEACHER"></property>
		<property name="studentId" column="STUDENTID"></property>
	</class>
</hibernate-mapping>

可以看出这里面定义的属性跟我给出的表结构是完全对应的。
5.2 给出我的Grade类的实现：

package com.neuqsoft.model;
public class Grade {
  private String id;
  private String subject;
  private  float grade;
  private   String teacher;
  private   String studentId;
public String getId() {
	return id;
}
public void setId(String id) {
	this.id = id;
}
public String getSubject() {
	return subject;
}
public void setSubject(String subject) {
	this.subject = subject;
}
public float getGrade() {
	return grade;
}
public void setGrade(float grade) {
	this.grade = grade;
}
public String getTeacher() {
	return teacher;
}
public void setTeacher(String teacher) {
	this.teacher = teacher;
}
public String getStudentId() {
	return studentId;
}
public void setStudentId(String studentId) {
	this.studentId = studentId;
}
  
}

5.3 根据HibernateSessionFactory.java提供的方法，自己生成了一个CRUD类，供后面自己使用起来方便简单，本工程的目录结构通过相应的包名都能看出来。

package com.neuqsoft.crud;

import org.hibernate.*;
import com.neuqsoft.model.Grade;
import com.neuqsoft.hibernate.HibernateSessionFactory;
import java.util.*;
public class CRUD {
	private Session session;
	private Transaction ts;
    //构造函数初始化session和事务
	public CRUD() {
		session = HibernateSessionFactory.getSession();
		ts = session.beginTransaction();
	}
   //添加
	public void insert(Grade grade) {
		session.save(grade);
	}
   // 删除，通过ID
	public void delete(Grade grade) {
		session.delete(grade);
	}
	//删除通过HQL
    public int deletebyHQL(String hql){
    	Query query=session.createQuery(hql);
    	int ref=query.executeUpdate();
    	return ref;
    }
    //查询ByCretria
    public List<Grade> queryByCriteria(Criteria c){
    	List<Grade> list=c.list();
    	return list;
    }
    //查询ByHQL
    public List<Grade> queryByHQL(String hql){
    	Query query=session.createQuery(hql);
    	List<Grade> list=query.list();
    	return list;
    }
    //修改
    public void update(Grade grade){
    	 session.update(grade);
    }
    
    //提交事务，关闭session
	public void commit() {
		ts.commit();
			}
	public void close(){
		session.close();
	}
	//重新开启事务：
	public  void  restartTransaction(){
		ts = session.beginTransaction();
	}
	//获取session
	public Session getSession(){
		return HibernateSessionFactory.getSession();
	}
	
}

5.4 下面给出真正的测试用类，这里提供的每一个方法都能单独使用，我这里全部写到一起了，一起执行也没问题的。

package com.neuqsoft.crud;
import com.neuqsoft.model.*;
import org.hibernate.Criteria;
import org.hibernate.criterion.Expression;
import java.util.*;
public class CrudTest {
 public static void main(String args[]){
	 CRUD crud=new CRUD();
	 Grade grade=new Grade();
	 //1.新增一个grade记录到数据库中
	 grade.setId("25");
	 grade.setSubject("testsubject");
	 grade.setGrade((float)52.25);
	 grade.setTeacher("MIss liu");
	 grade.setStudentId("050104010125");
	 crud.insert(grade);
	 crud.commit();
	 System.out.println("成功插入一条记录");
	 //2.删除记录byID
	 crud.restartTransaction();
	 Grade grade1=new Grade();
	 grade1.setId("20");
	 crud.delete(grade1);
	 crud.commit();
	 System.out.println("成功通过ID删除一条记录");
	 //3.删除记录BYHQL
	 crud.restartTransaction();
	 String hql="delete Grade where teacher like 'MIss%'";
	 int ref=crud.deletebyHQL(hql);
	 crud.commit();
	 System.out.println("通过HQL已成功删除："+ref+"条");
	 // 4.查询使用criteria
	 Criteria criteria=crud.getSession().createCriteria(Grade.class);
	 criteria.add(Expression.lt("teacher","Miss_zhang"));
	 List<Grade> list=crud.queryByCriteria(criteria);
	 for (int i=0;i<list.size();i++){
		 System.out.println(list.get(i).getId()+" "
			+list.get(i).getSubject()+" "
			+list.get(i).getGrade()+" "
			+list.get(i).getTeacher()+" "
			+list.get(i).getStudentId());
	 }
	 System.out.println();
	 //5.查询使用HQL
	 List<Grade> list1=crud.queryByHQL(" from  Grade");
	 for (int i=0;i<list1.size();i++){
		 System.out.println(list1.get(i).getId()+" "
			+list1.get(i).getSubject()+" "
			+list1.get(i).getGrade()+" "
			+list1.get(i).getTeacher()+" "
			+list1.get(i).getStudentId());
	 }
	 //6.更新,通过ID更新，按ID找到行，将grade改为相应的值，其他值不变。
	 crud.restartTransaction();
	 Grade grade2=(Grade)crud.getSession().get(Grade.class,"3");
	 grade2.setGrade((float)99.9);
	 crud.update(grade2);
	 crud.commit();
	 System.out.println("/n成功更新");
	 //7.关闭session
	 crud.close();
 } 
}

5.5 最后的hibernate.cfg.xml文件是这样的：

<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
          "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
          "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<!-- Generated by MyEclipse Hibernate Tools.                   -->
<hibernate-configuration>
	<session-factory>
		<property name="connection.username">scott</property>
		<property name="connection.url">
			jdbc:oracle:thin:@127.0.0.1:1521:orcl
		</property>
		<property name="connection.password">test</property>
		<property name="connection.driver_class">
			oracle.jdbc.driver.OracleDriver
		</property>
		<mapping resource="Grade.hbm.xml" />
	</session-factory>
</hibernate-configuration>

六、实际上hibernate并不像想象的那么神秘，不是Hibernate总是跟struts，spring捆绑的它是自成一体的，为面向对象的访问数据库提供了很好的
支持。另外还可以看出通过Myeclipse能够大大提高我们基于Hibernate持久层的C/S结构的程序开发效率，不是只有B/S才能用Hibernate呦！
七、还是给出目录结构吧，最近优快云不让传图了，就用文本表示吧。

src
  com.neuqsoft.crud
	    CURD.java
	    CurdTest.java
  com.neqsoft.hibernate
	    HibernateSessionFactory.java
  com.nequsoft.model
	    Grade.java
  hibernate.cfg.xml
  Grade.hbm.xml

八、结束。