[Java知识库]hibernate入门

一、hibernate简介

（可随意切换数据库）

ORM框架/持久层框架? ? ? ? jdbc的一个框架

object reference mapping? ? ? ? 对象映射关系

通过管理对象来改变数据库中的数据

通过管理对象来操作数据库

优势：跨数据库的无缝移植（无需写数据库，底层生成）

二、hibernate使用

1.新建一个maven项目

2.导入hibernate依赖

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>zw.com</groupId>
  <artifactId>zw_hibernate</artifactId>
  <packaging>war</packaging>
  <version>0.0.1-SNAPSHOT</version>
  <name>zw_hibernate Maven Webapp</name>
  <url>http://maven.apache.org</url>
  
  <properties>
	<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
	<maven.compiler.source>1.8</maven.compiler.source>
	<maven.compiler.target>1.8</maven.compiler.target>
	<junit.version>4.12</junit.version>
	<servlet.version>4.0.0</servlet.version>
	<hibernate.version>5.3.0.Final</hibernate.version>
	<mysql.driver.version>8.0.19</mysql.driver.version>
</properties>
  
  <dependencies>
    <dependency>
		<groupId>junit</groupId>
		<artifactId>junit</artifactId>
		<version>${junit.version}</version>
		<scope>test</scope>
	</dependency>

	<dependency>
		<groupId>javax.servlet</groupId>
		<artifactId>javax.servlet-api</artifactId>
		<version>${servlet.version}</version>
		<scope>provided</scope>
	</dependency>

	<dependency>
		<groupId>org.hibernate</groupId>
		<artifactId>hibernate-core</artifactId>
		<version>${hibernate.version}</version>
	</dependency>

	<dependency>
		<groupId>mysql</groupId>
		<artifactId>mysql-connector-java</artifactId>
		<version>${mysql.driver.version}</version>
	</dependency>
  </dependencies>
  <build>
    <finalName>zw_hibernate</finalName>
    
    <plugins>
        <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.7.0</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                    <encoding>UTF-8</encoding>
                </configuration>
            </plugin>
    </plugins>
    
  </build>
</project>

在pom.xml中导jar包依赖时，可能没下载完全，就可以按以下操作检查（可以解决90%jar包没下载完全的问题）：

先清除jar包：

?然年进行测试：

?表示pom文件没有写错?

3.找到框架的配置文件

在resource文件中新建xml文件，取名为hibernate.cfg.xml

?

?使用外部引用的方法在hibernate.cfg.xml文件中引入dtd约束

<?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>
        <!-- 1. 数据库相关5.7 -->
<!--         <property name="connection.username">root</property> -->
<!--         <property name="connection.password">123456</property> -->
<!--         <property name="connection.url">jdbc:mysql://47.100.191.44:3308/lx?useUnicode=true&amp;characterEncoding=UTF-8</property> -->
<!--         <property name="connection.driver_class">com.mysql.jdbc.Driver</property> -->
        <!-- 1. 数据库相关8.0 -->
        <property name="connection.username">root</property>
        <property name="connection.password">123456</property>
        <property name="connection.url">jdbc:mysql://127.0.0.1:3306/mybatis_ssm?useUnicode=true&amp;characterEncoding=utf8&amp;serverTimezone=GMT&amp;useSSL=true</property>
        <property name="connection.driver_class">com.mysql.cj.jdbc.Driver</property>
        <property name="dialect">org.hibernate.dialect.MySQLDialect</property>
        <!-- <property name="dialect">org.hibernate.dialect.Oracle10gDialect</property> -->

        <!-- 配置本地事务（No CurrentSessionContext configured!） -->
        <property name="hibernate.current_session_context_class">thread</property>

        <!-- 2. 调试相关 -->
        <property name="show_sql">true</property>
        <property name="format_sql">true</property>
        <!-- 配置映射文件 -->
        <mapping resource="com/one/entity/User.hbm.xml" />

        <!-- 主键生成策略 -->
<!--         <mapping resource="com/zking/two/entity/Student.hbm.xml" /> -->
<!--         <mapping resource="com/zking/two/entity/Worker.hbm.xml" /> -->

        <!-- 一对多 -->
<!--         <mapping resource="com/zking/four/entity/Order.hbm.xml" /> -->
<!--         <mapping resource="com/zking/four/entity/OrderItem.hbm.xml" /> -->
        <!-- 一对多的自关联 -->
<!--         <mapping resource="com/zking/five/entity/TreeNode.hbm.xml" /> -->

        <!-- 多对多 -->
<!--         <mapping resource="com/zking/five/entity/Category.hbm.xml" /> -->
<!--         <mapping resource="com/zking/five/entity/Book.hbm.xml" /> -->
    </session-factory>
</hibernate-configuration>

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC 
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
	 <class name="com.zking.one.entity.User" table="t_hibernate_user">
        <id name="id" type="java.lang.Integer" column="id">
            <generator class="increment" />
        </id>
        <property name="userName" type="java.lang.String" column="user_name">
        </property>
        <property name="userPwd" type="java.lang.String" column="user_pwd">
        </property>
        <property name="realName" type="java.lang.String" column="real_name">
        </property>
        <property name="sex" type="java.lang.String" column="sex">
        </property>
        <property name="birthday" type="java.sql.Date" column="birthday">
        </property>
        <property insert="false" update="false" name="createDatetime"
            type="java.sql.Timestamp" column="create_datetime">
        </property>
        <property name="remark" type="java.lang.String" column="remark">
        </property>
    </class>
</hibernate-mapping>

user类：

public class User {
    private int id;
    private String userName;
    private String userPwd;
    private String realName;
    private String sex;
    private Date birthday;
    private Timestamp createDatetime;
    private String remark;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getUserName() {
        return userName;
    }
    public void setUserName(String userName) {
        this.userName = userName;
    }
    public String getUserPwd() {
        return userPwd;
    }
    public void setUserPwd(String userPwd) {
        this.userPwd = userPwd;
    }
    public String getRealName() {
        return realName;
    }
    public void setRealName(String realName) {
        this.realName = realName;
    }
    public String getSex() {
        return sex;
    }
    public void setSex(String sex) {
        this.sex = sex;
    }
    public Date getBirthday() {
        return birthday;
    }
    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }
    public Timestamp getCreateDatetime() {
        return createDatetime;
    }
    public void setCreateDatetime(Timestamp createDatetime) {
        this.createDatetime = createDatetime;
    }
    public String getRemark() {
        return remark;
    }
    public void setRemark(String remark) {
        this.remark = remark;
    }
    @Override
    public String toString() {
        return "User [id=" + id + ", userName=" + userName + ", userPwd=" + userPwd + ", realName=" + realName
                + ", sex=" + sex + ", birthday=" + birthday + ", createDatetime=" + createDatetime + ", remark="
                + remark + "]";
    }

}

还需要写实体类的映射文件及测试代码

三、hibernate的使用

????????1、对框架核心配置文件（hibernate.cfg.xml）进行建模

? ? ? ? 2、获取sessionFactory工厂

? ? ? ? 3、获取session会话

? ? ? ? 4、开启事务（查询不需要事务）

? ? ? ? 5、session操作对象

? ? ? ? 6、提交事务（查询不需要事务）

? ? ? ? 7、关闭session

查询：

public class QueryDemo {
    public static void main(String[] args) {
        /*1、对框架核心配置文件进行建模       
        2、获取sessionFactory工厂       
        3、获取session会话       
        4、开启事务（查询不需要事务）        
        5、session操作对象       
        6、提交事务（查询不需要事务）        
        7、关闭session*/
        Configuration configure = new Configuration().configure("/hibernate.cfg.xml");
        SessionFactory sessionFactory = configure.buildSessionFactory();
        Session session = sessionFactory.openSession();
        List list = session.createQuery("from User").list();
        for(Object object:list) {
            System.out.println(object);
        }
        session.close();
    }

}

得到数据：

AddDemo:

?

public class AddDemo {
    public static void main(String[] args) {
        /*1、对框架核心配置文件进行建模       
        2、获取sessionFactory工厂       
        3、获取session会话       
        4、开启事务（查询不需要事务）        
        5、session操作对象       
        6、提交事务（查询不需要事务）        
        7、关闭session*/
        Configuration configure = new Configuration().configure("/hibernate.cfg.xml");
        SessionFactory sessionFactory = configure.buildSessionFactory();
        Session session = sessionFactory.openSession();
        Transaction transaction = session.beginTransaction();
        User user=new User();
        user.setBirthday(new Date(System.currentTimeMillis()));
        user.setCreateDatetime(new Timestamp(System.currentTimeMillis()));
        user.setId(55);
        user.setRealName("小熊");
        user.setRemark("武侠");
        user.setSex("男");
        user.setUserName("yiyi");
        user.setUserPwd("123456");
        session.save(user);
        transaction.commit();
        session.close();
    }

}

修改EditDemo:

public class EditDemo {
    public static void main(String[] args) {
        /*1、对框架核心配置文件进行建模       
        2、获取sessionFactory工厂       
        3、获取session会话       
        4、开启事务（查询不需要事务）        
        5、session操作对象       
        6、提交事务（查询不需要事务）        
        7、关闭session*/
        Configuration configure = new Configuration().configure("/hibernate.cfg.xml");
        SessionFactory sessionFactory = configure.buildSessionFactory();
        Session session = sessionFactory.openSession();
        Transaction transaction = session.beginTransaction();
//        拿到数据
        User user = session.get(User.class, 55);
//        修改数据
        user.setRealName("toto");
        System.out.println(user);
        
        transaction.commit();
        session.close();
    }

}

删除DelDemo:

public class DelDemo {
    public static void main(String[] args) {
        /*1、对框架核心配置文件进行建模       
        2、获取sessionFactory工厂       
        3、获取session会话       
        4、开启事务（查询不需要事务）        
        5、session操作对象       
        6、提交事务（查询不需要事务）        
        7、关闭session*/
        Configuration configure = new Configuration().configure("/hibernate.cfg.xml");
        SessionFactory sessionFactory = configure.buildSessionFactory();
        Session session = sessionFactory.openSession();
        Transaction transaction = session.beginTransaction();
//        拿到数据
        User user = session.get(User.class, 55);
//        修改数据
        session.delete(user);
        transaction.commit();
        session.close();
    }

?