转自: http://blog.csdn.net/fover717/article/details/8334209
http://www.cnblogs.com/zemliu/archive/2013/08/07/3242966.html
http://fhd001.iteye.com/blog/1121189
参考:http://blog.csdn.net/isea533/article/details/23831273
http://blog.csdn.net/hupanfeng/article/details/9238127
1.MyBatis 例子
首先,单独使用MyBatis时:
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- import java.io.IOException;
- import java.io.Reader;
- import org.apache.ibatis.io.Resources;
- import org.apache.ibatis.session.SqlSessionFactory;
- import org.apache.ibatis.session.SqlSessionFactoryBuilder;
- public class MyBatisUtil {
- // 每一个MyBatis的应用程序都以一个SqlSessionFactory对象的实例为核心
- // 使用SqlSessionFactory的最佳实践是在应用运行期间不要重复创建多次,最佳范围是应用范围
- private final static SqlSessionFactory sqlSessionFactory;
- static {
- String resource = "configuration.xml";
- Reader reader = null;
- try {
- reader = Resources.getResourceAsReader(resource);
- } catch (IOException e) {
- System.out.println(e.getMessage());
- }
- // SqlSessionFactory对象的实例可以通过SqlSessionFactoryBuilder对象来获得
- // SqlSessionFactoryBuilder实例的最佳范围是方法范围(也就是本地方法变量)。
- sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
- }
- public static SqlSessionFactory getSqlSessionFactory() {
- return sqlSessionFactory;
- }
- }
配置文件:
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- <?xml version="1.0" encoding="UTF-8" ?>
- <!DOCTYPE mapper
- PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
- "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
- <mapper namespace="Mapper.UserMapper">
- <!-- 这里namespace必须是UserMapper接口的路径,不然要运行的时候要报错 “is not known to the MapperRegistry”-->
- <insert id="insertUser" parameterType="User">
- insert into vincent_user(name,age) values(#{name},#{age})
- <!-- 这里sql结尾不能加分号,否则报“ORA-00911”的错误 -->
- </insert>
- <!-- 这里的id必须和UserMapper接口中的接口方法名相同,不然运行的时候也要报错 -->
- <select id="getUser" resultType="User" parameterType="java.lang.String">
- select * from vincent_user where name=#{name}
- </select>
- </mapper>
使用的测试类为:
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- import org.apache.ibatis.session.SqlSession;
- import org.apache.ibatis.session.SqlSessionFactory;
- import org.junit.Test;
- public class TestMapper {
- static SqlSessionFactory sqlSessionFactory = null;
- static {
- sqlSessionFactory = MyBatisUtil.getSqlSessionFactory();
- }
- @Test
- public void testAdd() {
- SqlSession sqlSession = sqlSessionFactory.openSession();
- try {
- UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
- User user = new User("tom",new Integer(5));
- userMapper.insertUser(user);
- sqlSession.commit();//这里一定要提交,不然数据进不去数据库中
- } finally {
- sqlSession.close();
- }
- }
- @Test
- public void getUser() {
- SqlSession sqlSession = sqlSessionFactory.openSession();
- try {
- UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
- User user = userMapper.getUser("jun");
- System.out.println("name: "+user.getName()+"|age: "+user.getAge());
- } finally {
- sqlSession.close();
- }
- }
- }
2.整合Spring3后,单独使用Mybatis
首先,Spring3配置文件中(applicationContext.xml)有:
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- <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
- <property name="configLocation" value="classpath:ibatis-config.xml" />
- <property name="dataSource" ref="dataSource" />
- <!-- mapper和resultmap配置路径 -->
- <property name="mapperLocations">
- <span style="white-space:pre"> </span><list>
- <span style="white-space:pre"> </span><value>classpath:com/log/bean/mapper/*.xml</value>
- <span style="white-space:pre"> </span></list>
- </property>
- </bean>
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- <!-- 通过扫描的模式,扫描目录在com/log/bean/mapper目录下,所有的mapper都继承
- SQLMapper接口的接口, 这样一个bean就可以了 -->
- <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
- <property name="basePackage" value="com.log.bean.mapper"/>
- <property name="markerInterface" value="com.log.bean.mapper.SQLMapper"/>
- </bean>
工具类:
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- import org.apache.ibatis.session.SqlSessionFactory;
- import org.springframework.context.ApplicationContext;
- import org.springframework.context.support.FileSystemXmlApplicationContext;
- public class MyBatisUtil {
- private final static SqlSessionFactory sqlSessionFactory;
- static {
- ApplicationContext ac = new FileSystemXmlApplicationContext("classpath:applicationContext.xml");
- sqlSessionFactory = (SqlSessionFactory)ac.getBean("sqlSessionFactory");
- }
- public static SqlSessionFactory getSqlSessionFactory() {
- return sqlSessionFactory;
- }
- }
myBatis3之从SqlSessionFactory中获取SqlSession
----------
现在,我们已经知道如何获取SqlSessionFactory对象了,基于同样的启示,我们就可以获得SqlSession的实例了。SqlSession对象完全包含以数据库为背景的所有执行SQL操作的方法。你可以用SqlSession实例来直接执行已映射的SQL 语句。例如:
Java代码
- SqlSession session = sqlMapper.openSession();
- try{
- Blog blog = (Blog)session.selectOne("org.mybatis.example.BlogMapper.selectBlog",101);
- }finally{
- session.close();
- }
现在有一种更简洁的方法。使用合理描述参数和SQL语句返回值的接口(比如BlogMapper.class),这样现在就更简单,更安全的代码,没有容易发生的字符串文字和转换的错误。例如:
Java代码
- SqlSession session = sqlSessionFactory.openSession();
- try {
- BlogMapper mapper = session.getMapper(BlogMapper.class);
- Blog blog = mapper.selectBlog(101);
- }finally{
- session.close();
- }
探究已映射的SQL语句
这里给出一个基于XML映射语句的示例,这些语句应该可以满足上述示例中SqlSession对象的调用。
Xml代码
- <?xml version="1.0" encoding="UTF-8" ?>
- <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
- "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
- <mapper namespace="org.mybatis.example.BlogMapper">
- <select id="selectBlog" parameterType="int" resultType="Blog">
- select * from Blog where id = #{id}
- </select>
- </mapper>
在命名空间“com.mybatis.example.BlogMapper”中,它定义了一个名为“selectBlog”的映射语句,这样它允许你使用完全限定名“org.mybatis.example.BlogMapper.selectBlog”来调用映射语句,我们下面示例中的写法也就是这样的。
Java代码
- Blog blog = (Blog)session.selectOne("org.mybatis.example.BlogMapper.selectBlog", 101);
但下面的调用更有优势:
映射接口对应映射xml文件的命令空间,接口方法对应映射xml文件中定义的SQL映射的ID。???????????
Java代码
- BlogMapper mapper = session.getMapper(BlogMapper.class);
- Blog blog = mapper.selectBlog(101);
首先它不是基于文字的,那就更安全了。第二,如果你的IDE有代码补全功能,那么你可以利用它来操纵已映射的SQL语句。第三,不需要强制类型转换,同时BlogMapper接口可以保持简洁,返回值类型很安全(参数类型也很安全);
MyBatis 物理分页
MyBatis使用RowBounds实现的分页是逻辑分页,也就是先把数据记录全部查询出来,然在再根据offset和limit截断记录返回
为了在数据库层面上实现物理分页,又不改变原来MyBatis的函数逻辑,可以编写plugin截获MyBatis Executor的statementhandler,重写SQL来执行查询
参考资料: http://blog.csdn.net/hupanfeng/article/details/9265341
下面的插件代码只针对MySQL
plugin代码
package plugin; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.util.Properties; import org.apache.ibatis.executor.parameter.ParameterHandler; import org.apache.ibatis.executor.statement.StatementHandler; import org.apache.ibatis.logging.Log; import org.apache.ibatis.logging.LogFactory; import org.apache.ibatis.mapping.BoundSql; import org.apache.ibatis.mapping.MappedStatement; import org.apache.ibatis.plugin.Interceptor; import org.apache.ibatis.plugin.Intercepts; import org.apache.ibatis.plugin.Invocation; import org.apache.ibatis.plugin.Plugin; import org.apache.ibatis.plugin.Signature; import org.apache.ibatis.reflection.MetaObject; import org.apache.ibatis.reflection.factory.DefaultObjectFactory; import org.apache.ibatis.reflection.factory.ObjectFactory; import org.apache.ibatis.reflection.wrapper.DefaultObjectWrapperFactory; import org.apache.ibatis.reflection.wrapper.ObjectWrapperFactory; import org.apache.ibatis.scripting.defaults.DefaultParameterHandler; import org.apache.ibatis.session.Configuration; import org.apache.ibatis.session.RowBounds; /** * 通过拦截<code>StatementHandler</code>的<code>prepare</code>方法,重写sql语句实现物理分页。 * 老规矩,签名里要拦截的类型只能是接口。 * */ @Intercepts({@Signature(type = StatementHandler.class, method = "prepare", args = {Connection.class})}) public class PaginationInterceptor implements Interceptor { private static final Log logger = LogFactory.getLog(PaginationInterceptor.class); private static final ObjectFactory DEFAULT_OBJECT_FACTORY = new DefaultObjectFactory(); private static final ObjectWrapperFactory DEFAULT_OBJECT_WRAPPER_FACTORY = new DefaultObjectWrapperFactory(); private static String DEFAULT_PAGE_SQL_ID = ".*Page$"; // 需要拦截的ID(正则匹配) @Override public Object intercept(Invocation invocation) throws Throwable { StatementHandler statementHandler = (StatementHandler) invocation.getTarget(); MetaObject metaStatementHandler = MetaObject.forObject(statementHandler, DEFAULT_OBJECT_FACTORY, DEFAULT_OBJECT_WRAPPER_FACTORY); RowBounds rowBounds = (RowBounds) metaStatementHandler.getValue("delegate.rowBounds"); // 分离代理对象链(由于目标类可能被多个拦截器拦截,从而形成多次代理,通过下面的两次循环可以分离出最原始的的目标类) while (metaStatementHandler.hasGetter("h")) { Object object = metaStatementHandler.getValue("h"); metaStatementHandler = MetaObject.forObject(object, DEFAULT_OBJECT_FACTORY, DEFAULT_OBJECT_WRAPPER_FACTORY); } // 分离最后一个代理对象的目标类 while (metaStatementHandler.hasGetter("target")) { Object object = metaStatementHandler.getValue("target"); metaStatementHandler = MetaObject.forObject(object, DEFAULT_OBJECT_FACTORY, DEFAULT_OBJECT_WRAPPER_FACTORY); } // property在mybatis settings文件内配置 Configuration configuration = (Configuration) metaStatementHandler.getValue("delegate.configuration"); // 设置pageSqlId String pageSqlId = configuration.getVariables().getProperty("pageSqlId"); if (null == pageSqlId || "".equals(pageSqlId)) { logger.warn("Property pageSqlId is not setted,use default ‘.*Page$‘ "); pageSqlId = DEFAULT_PAGE_SQL_ID; } MappedStatement mappedStatement = (MappedStatement) metaStatementHandler.getValue("delegate.mappedStatement"); // 只重写需要分页的sql语句。通过MappedStatement的ID匹配,默认重写以Page结尾的MappedStatement的sql if (mappedStatement.getId().matches(pageSqlId)) { BoundSql boundSql = (BoundSql) metaStatementHandler.getValue("delegate.boundSql"); Object parameterObject = boundSql.getParameterObject(); if (parameterObject == null) { throw new NullPointerException("parameterObject is null!"); } else { String sql = boundSql.getSql(); // 重写sql String pageSql = sql + " LIMIT " + rowBounds.getOffset() + "," + rowBounds.getLimit(); metaStatementHandler.setValue("delegate.boundSql.sql", pageSql); // 采用物理分页后,就不需要mybatis的内存分页了,所以重置下面的两个参数 metaStatementHandler.setValue("delegate.rowBounds.offset", RowBounds.NO_ROW_OFFSET); metaStatementHandler.setValue("delegate.rowBounds.limit", RowBounds.NO_ROW_LIMIT); } } // 将执行权交给下一个拦截器 return invocation.proceed(); } @Override public Object plugin(Object target) { // 当目标类是StatementHandler类型时,才包装目标类,否者直接返回目标本身,减少目标被代理的次数 if (target instanceof StatementHandler) { return Plugin.wrap(target, this); } else { return target; } } @Override public void setProperties(Properties properties) { //To change body of implemented methods use File | Settings | File Templates. } }
配置plugin
<plugins> <plugin interceptor="plugin.PaginationInterceptor" /> </plugins>
查询SQL
<!-- 测试分页查询 --> <select id="selectUserByPage" resultMap="dao.base.userResultMap"> <![CDATA[ SELECT * FROM user ]]> </select>
调用示例
@Override public List<User> selectUserByPage(int offset, int limit) { RowBounds rowBounds = new RowBounds(offset, limit); return getSqlSession().selectList("dao.userdao.selectUserByPage", new Object(), rowBounds); }
另外,结合Spring MVC,编写翻页和生成页码代码
页码类
package util; /** * Created with IntelliJ IDEA. * User: zhenwei.liu * Date: 13-8-7 * Time: 上午10:29 * To change this template use File | Settings | File Templates. */ public class Pagination { private String url; // 页码url private int pageSize = 10; // 每页显示记录数 private int currentPage = 1; // 当前页码 private int maxPage = Integer.MAX_VALUE; // 最大页数 // 获取offset public int getOffset() { return (currentPage - 1) * pageSize; } // 获取limit public int getLimit() { return getPageSize(); } public String getUrl() { return url; } public void setUrl(String url) { this.url = url; } public int getPageSize() { return pageSize; } public void setPageSize(int pageSize) { this.pageSize = pageSize; } public int getCurrentPage() { return currentPage; } public void setCurrentPage(int currentPage) { if (currentPage < 1) currentPage = 1; if (currentPage > maxPage) currentPage = maxPage; this.currentPage = currentPage; } public int getMaxPage() { return maxPage; } public void setMaxPage(int maxPage) { this.maxPage = maxPage; } }
为了计算最大页码,需要知道数据表的总记录数,查询SQL如下
<!-- 记录总数 --> <select id="countUser" resultType="Integer"> <![CDATA[ SELECT COUNT(*) FROM user ]]> </select>
@Override public Integer countTable() { return getSqlSession().selectOne("dao.userdao.countUser"); }
Controller中的使用
@RequestMapping("/getUserByPage") public String getUserByPage(@RequestParam int page, Model model) { pagination.setCurrentPage(page); pagination.setUrl(getCurrentUrl()); pagination.setMaxPage(userDao.countTable() / pagination.getPageSize() + 1); List<User> userList = userDao.selectUserByPage( pagination.getOffset(), pagination.getLimit()); model.addAttribute(pagination); model.addAttribute(userList); return "index"; }