CRUD是指在做計算處理時的增加(Create)、讀取(Retrieve)（重新得到數(shù)據(jù)）、更新(Update)和刪除(Delete)幾個單詞的首字母簡寫.
下面列舉實(shí)例來講解這幾個操作：
實(shí)體類：
package com.oumyye.model;public class Student { PRivate long id; private String name; private Class c; public long getId() { return id; } public void setId(long id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Class getC() { return c; } public void setC(Class c) { this.c = c; } @Override public String toString() { return "Student [id=" + id + ", name=" + name + "]"; } }package com.oumyye.model;import java.util.HashSet;import java.util.Set;public class Class { private long id; private String name; private Set<Student> students=new HashSet<Student>(); public long getId() { return id; } public void setId(long 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; } }映射文件：
Student.hbm.xml
<?xml version="1.0"?><!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"><hibernate-mapping package="com.oumyye.model"> <class name="Student" table="t_student"> <id column="stuId" name="id"> <generator class="native"/> </id> <property column="stuName" generated="never" lazy="false" name="name"/> <many-to-one cascade="save-update" class="com.oumyye.model.Class" column="classId" name="c"/> </class></hibernate-mapping>
Class.hbm.xml
<?xml version="1.0"?><!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"><hibernate-mapping package="com.oumyye.model"> <class name="Class" table="t_class"> <id column="classId" name="id"> <generator class="native"/> </id> <property column="className" generated="never" lazy="false" name="name"/> <set cascade="delete" inverse="true" name="students" sort="unsorted"> <key column="classId"/> <one-to-many class="com.oumyye.model.Student"/> </set> </class></hibernate-mapping>
工具類：可以有myeclipse生成
package com.oumyye.util;import org.hibernate.HibernateException;import org.hibernate.session;import org.hibernate.cfg.Configuration;import org.hibernate.cfg.AnnotationConfiguration;/** * 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 final ThreadLocal<Session> threadLocal = new ThreadLocal<Session>(); private static org.hibernate.SessionFactory sessionFactory; private static Configuration configuration = new AnnotationConfiguration(); private static String CONFIG_FILE_LOCATION = "/hibernate.cfg.xml"; 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; }}
配置文件hibernate.cfg.xml
<?xml version='1.0' encoding='utf-8'?><!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd"><hibernate-configuration><session-factory> <!--數(shù)據(jù)庫連接設(shè)置 --> <property name="connection.driver_class"> com.MySQL.jdbc.Driver </property> <property name="connection.url"> jdbc:mysql://localhost:3306/mytest </property> <property name="connection.username">root</property> <property name="connection.passWord">root</property> <!-- 方言 --> <property name="dialect"> org.hibernate.dialect.MySQL5Dialect </property> <!-- 控制臺顯示SQL --> <property name="show_sql">true</property> <!-- 自動更新表結(jié)構(gòu) --> <property name="hbm2ddl.auto">update</property> <mapping resource="com/oumyye/model/Class.hbm.xml" /> <mapping resource="com/oumyye/model/Student.hbm.xml" /></session-factory></hibernate-configuration>
測試類
package com.oumyye.service;import java.util.Iterator;import java.util.Set;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.junit.After;import org.junit.Before;import org.junit.Test;import com.oumyye.model.Class;import com.oumyye.model.Student;import com.oumyye.util.HibernateSessionFactory;public class StudentTest { private SessionFactory sessionFactory=HibernateSessionFactory.getSessionFactory(); private Session session; @Before public void setUp() throws Exception { session=sessionFactory.openSession(); // 生成一個session session.beginTransaction(); // 開啟事務(wù) } @After public void tearDown() throws Exception { session.getTransaction().commit(); // 提交事務(wù) session.close(); // 關(guān)閉session } @Test public void testSaveClassAndStudent() { Class c=new Class(); c.setName("08計本"); Student s1=new Student(); s1.setName("張三"); s1.setC(c); Student s2=new Student(); s2.setName("李四"); s2.setC(c); session.save(s1); session.save(s2); } @Test public void testLoadClass(){ // Class c=(Class)session.load(Class.class, Long.valueOf(2)); Class c=(Class)session.load(Class.class, Long.valueOf(1)); System.out.println(c.getStudents()); } @Test public void testGetClass(){ // Class c=(Class)session.get(Class.class, Long.valueOf(2)); Class c=(Class)session.get(Class.class, Long.valueOf(1)); System.out.println(c.getStudents()); } @Test public void testUpdateClass(){ Session session1=sessionFactory.openSession(); session1.beginTransaction(); Class c=(Class)session1.get(Class.class, Long.valueOf(1)); session1.getTransaction().commit(); // 提交事務(wù) session1.close(); Session session2=sessionFactory.openSession(); session2.beginTransaction(); c.setName("08計算機(jī)本科2"); session2.update(c); session2.getTransaction().commit(); // 提交事務(wù) session2.close(); } <!--更新--> @Test public void testSaveOrUpdateClass(){ Session session1=sessionFactory.openSession(); session1.beginTransaction(); Class c=(Class)session1.get(Class.class, Long.valueOf(1)); session1.getTransaction().commit(); // 提交事務(wù) session1.close(); Session session2=sessionFactory.openSession(); session2.beginTransaction(); c.setName("08計算機(jī)本科3"); Class c2=new Class(); c2.setName("09計算機(jī)本科3"); session2.saveOrUpdate(c); session2.saveOrUpdate(c2); session2.getTransaction().commit(); // 提交事務(wù) session2.close(); } @Test public void testMergeClass(){ Session session1=sessionFactory.openSession(); session1.beginTransaction(); Class c=(Class)session1.get(Class.class, Long.valueOf(1)); session1.getTransaction().commit(); // 提交事務(wù) session1.close(); Session session2=sessionFactory.openSession(); session2.beginTransaction(); Class c2=(Class)session2.get(Class.class, Long.valueOf(1)); c.setName("08計算機(jī)本科4"); session2.merge(c); session2.getTransaction().commit(); // 提交事務(wù) session2.close(); } <!--刪除--> @Test public void testDeleteStudent(){ Student student=(Student)session.load(Student.class, Long.valueOf(1)); session.delete(student); }}Session的入門常用方法新聞熱點(diǎn)
疑難解答
