java实战应用：MyBatis实现单表的增删改

MyBatis 是支持普通 SQL查询，存储过程和高级映射的优秀持久层框架。MyBatis 消除了几乎所有的JDBC代码和参数的手工设置以及结果集的检索。MyBatis 使用简单的 XML或注解用于配置和原始映射，将接口和 Java 的POJOs（Plain Old Java Objects，普通的 Java对象）映射成数据库中的记录。
每个MyBatis应用程序主要都是使用SqlSessionFactory实例的，一个SqlSessionFactory实例可以通过SqlSessionFactoryBuilder获得。SqlSessionFactoryBuilder可以从一个xml配置文件或者一个预定义的配置类的实例获得。
用xml文件构建SqlSessionFactory实例是非常简单的事情。推荐在这个配置中使用类路径资源（classpath resource)，但你可以使用任何Reader实例，包括用文件路径或file://开头的url创建的实例。MyBatis有一个实用类----Resources，它有很多方法，可以方便地从类路径及其它位置加载资源。

 一、首先建立项目的整体效果图：

以下是MyBatis单表的增删改：

二、项目代码：
1）实体类：News中：

public class News {
	private Integer id;
	private String title;
	private String content;
	private Date pubDate;
	private Integer typeId;
	private String photo;
	private String tname;
	//get,set方式省去

2）dao层借口层的INewsDAO：

import java.util.List;
import java.util.Map;
import org.liky.vo.News;

public interface INewsDAO {

	public void doCreate(News news) throws Exception;
	public void doUpdate(News news) throws Exception;
	public void doRemove(int id) throws Exception;
	public List<News> findAll() throws Exception;
	public News findById(int id) throws Exception;
	public List<News> findAllSplit(Map<String, Object> map) throws Exception;
	public int getAllCount(Map<String, Object> map) throws Exception;

}

3)dao层的实现，INewDAO.xml，正常不是myBatis,这里是写dao层的实现类的：myBatis的优势也是在这里，将sql语句抽调出来单独写入到一个xml中，便于管理数据库。它是更接近于jdbc的，所以处理的速度很快，它是外网项目中需要用到框架。

<mapper namespace="org.liky.dao.INewsDAO">

	<resultMap type="News" id="NewsResult">
		<id column="id" property="id" />
		<result column="title" property="title" />
		<result column="content" property="content" />
		<result column="pub_date" property="pubDate" />
		<result column="type_id" property="typeId" />
		<result column="photo" property="photo" />
	</resultMap>

	<insert id="doCreate" parameterType="News">
		INSERT INTO news
		(id,title,content,pub_date,type_id,photo) VALUES
		(news_seq.nextVal,#{title},#{content},#{pubDate},#{typeId},#{photo})
	</insert>

	<update id="doUpdate" parameterType="News">
		UPDATE news
		SET title =
		#{title},content=#{content},pub_date = #{pubDate},type_id =
		#{typeId},photo=#{photo}
		WHERE id = #{id}
	</update>

	<delete id="doRemove" parameterType="java.lang.Integer">
		DELETE FROM news WHERE id =
		#{id}
	</delete>

	<select id="findAll" resultMap="NewsResult">
		SELECT * FROM news
	</select>

	<select id="findById" resultType="News" parameterType="java.lang.Integer">
		SELECT
		id,title,content,pub_date AS pubDate,type_id AS typeId,photo,tname FROM news n,news_type nt
		WHERE id = #{id} AND n.type_id = nt.tid
	</select>

	<select id="findAllSplit" resultType="News" parameterType="java.util.Map">
		SELECT temp.* FROM (SELECT
		id,title,content,pub_date
		AS pubDate,type_id
		AS typeId,photo,ROWNUM rn
		FROM news WHERE ${column}
		LIKE #{keyword} AND
		ROWNUM <= #{endNumber}) temp WHERE temp.rn >
		#{startNumber}		 
	</select>

	<select id="getAllCount" resultType="int" parameterType="java.util.Map">
		SELECT
		COUNT(*) FROM news WHERE ${column} LIKE #{keyword}
	</select>

</mapper>

4)这一步可以写mybatis的总配置文件，初始加载连接数据库。

<configuration>
	<typeAliases>
		<package name="org.liky.vo" />
	</typeAliases>
	<environments default="development">
		<environment id="development">
			<transactionManager type="JDBC" />
			<dataSource type="POOLED">
				<property name="driver" value="oracle.jdbc.driver.OracleDriver" />
				<property name="url" value="jdbc:oracle:thin:@localhost:1521:ORCL" />
				<property name="username" value="sunxun" />
				<property name="password" value="123" />
			</dataSource>
		</environment>
	</environments>
	<mappers>
		<mapper resource="org/liky/dao/INewsDAO.xml" />
	</mappers>
</configuration>

5）建立MyBATISSqlSessionFactory类：

import java.io.InputStream;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

public class MyBATISSqlSessionFactory {

	// 配置文件的所在位置和名称
	private static String CONFIG_FILE_LOCATION = "mybatis-config.xml";

	// 用来实现连接池的，该类类似Map集合。
	private static final ThreadLocal<SqlSession> threadLocal = new ThreadLocal<SqlSession>();
	// Hibernate用来读取配置文件的类
	private static InputStream is;
	// 用来建立连接的，该类就是连接池，使用单例设计模式
	private static SqlSessionFactory sqlsessionFactory;
	// 备用的配置文件位置
	private static String configFile = CONFIG_FILE_LOCATION;

	// 静态块，类加载时最先执行
	static {
		try {
			// 加载配置文件到内存中
			is = Resources.getResourceAsStream(configFile);
			// 建立连接池以及里面的连接
			sqlsessionFactory = new SqlSessionFactoryBuilder().build(is);
		} catch (Exception e) {
			System.err.println("%%%% Error Creating SessionFactory %%%%");
			e.printStackTrace();
		}
	}

	private MyBATISSqlSessionFactory() {
	}

	/**
	 * 取得数据库连接对象
	 * 
	 * @return Session
	 * @throws HibernateException
	 */
	public static SqlSession getSession() {
		// 先从ThreadLocal中取得连接。
		SqlSession session = (SqlSession) threadLocal.get();

		// 如果手头没有连接，则取得一个新的连接
		if (session == null) {
			session = sqlsessionFactory.openSession();
			// 把取得出的连接记录到ThreadLocal中，以便下次使用。
			threadLocal.set(session);
		}
		return session;
	}

	/**
	 * 连接关闭的方法
	 * 
	 * @throws HibernateException
	 */
	public static void closeSession() {
		SqlSession session = (SqlSession) threadLocal.get();
		// 将ThreadLocal清空，表示当前线程已经没有连接。
		threadLocal.set(null);
		// 连接放回到连接池
		if (session != null) {
			session.close();
		}
	}
}

6）写service层实现的借口：

import java.util.List;
import java.util.Map;
import org.liky.vo.News;

public interface INewsService {

	public void insert(News news) throws Exception;

	public News findById(int id) throws Exception;

	public List<News> findAll() throws Exception;

	public Map<String, Object> list(int pageNo, int pageSize, String column,
			String keyword) throws Exception;

}

7）解耦合，写service的工厂：

import org.liky.service.INewsService;
import org.liky.service.impl.NewsServiceImpl;

public class ServiceFactory {

	public static INewsService getINewsServiceInstance() {
		return new NewsServiceImpl();
	}
}

8）service的实现类：

import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.liky.dao.INewsDAO;
import org.liky.dbc.MyBATISSqlSessionFactory;
import org.liky.service.INewsService;
import org.liky.vo.News;

public class NewsServiceImpl implements INewsService {

	public List<News> findAll() throws Exception {
		List<News> all = null;
		try {
			all = MyBATISSqlSessionFactory.getSession().getMapper(
					INewsDAO.class).findAll();
		} catch (Exception e) {
			e.printStackTrace();
			throw e;
		} finally {
			MyBATISSqlSessionFactory.closeSession();
		}
		return all;
	}

	public News findById(int id) throws Exception {
		News news = null;
		try {
			news = MyBATISSqlSessionFactory.getSession().getMapper(
					INewsDAO.class).findById(id);
		} catch (Exception e) {
			e.printStackTrace();
			throw e;
		} finally {
			MyBATISSqlSessionFactory.closeSession();
		}
		return news;
	}

	public void insert(News news) throws Exception {
		try {
			MyBATISSqlSessionFactory.getSession().getMapper(INewsDAO.class)
					.doCreate(news);
			MyBATISSqlSessionFactory.getSession().commit();
		} catch (Exception e) {
			e.printStackTrace();
			MyBATISSqlSessionFactory.getSession().rollback();
			throw e;
		} finally {
			MyBATISSqlSessionFactory.closeSession();
		}
	}

	public Map<String, Object> list(int pageNo, int pageSize, String column,
			String keyword) throws Exception {
		Map<String, Object> map = new HashMap<String, Object>();
		// 设置要向DAO中传递的参数
		Map<String, Object> params = new HashMap<String, Object>();
		params.put("column", column);
		params.put("keyword", "%" + keyword + "%");
		params.put("endNumber", pageNo * pageSize);
		params.put("startNumber", (pageNo - 1) * pageSize);
		try {
			map.put("allNews", MyBATISSqlSessionFactory.getSession().getMapper(
					INewsDAO.class).findAllSplit(params));
			map.put("count", MyBATISSqlSessionFactory.getSession().getMapper(
					INewsDAO.class).getAllCount(params));
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			MyBATISSqlSessionFactory.closeSession();
		}
		return map;
	}
}

9）测试类NewsServiceImplTest：

import java.util.Date;
import java.util.UUID;
import org.junit.Test;
import org.liky.factory.ServiceFactory;
import org.liky.vo.News;
public class NewsServiceImplTest {

	@Test
	public void testFindAll() throws Exception {
		System.out.println(ServiceFactory.getINewsServiceInstance().findAll());
	}

	@Test
	public void testFindById() throws Exception {
		System.out.println(ServiceFactory.getINewsServiceInstance()
				.findById(61).getTname());
	}

	@Test
	public void testInsert() throws Exception {
		News news = new News();
		news.setTitle("MyBATIS测试");
		news.setContent("MyBATIS添加测试");
		news.setTypeId(3);
		news.setPubDate(new Date());
		news.setPhoto(UUID.randomUUID().toString() + ".jpg");

		ServiceFactory.getINewsServiceInstance().insert(news);
	}

	@Test
	public void testListSplit() throws Exception {
		System.out.println(ServiceFactory.getINewsServiceInstance().list(1, 5,
				"title", ""));
	}
}

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