什么是 MyBatis ？
MyBatis 是支持定制化 SQL、存储过程以及高级映射的优秀的持久层框架。MyBatis 避免了几乎所有的 JDBC 代码和手动设置参数以及获取结果集。MyBatis 可以对配置和原生Map使用简单的 XML 或注解，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。
教程链接
https://mybatis.github.io/mybatis-3/zh/index.html
第一个helloworld程序源代码
①导入jar包
mybatis-3.2.8.jar
mysql-connector-java-5.1.18-bin.jar
②配置mybatis的配置文件Configuration.xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN""http://mybatis.org/dtd/mybatis-3-config.dtd"><configuration> <typeAliases> <typeAlias alias="User" type="com.oracle.pojo.User"/> </typeAliases><!--environments 可以填两种值
development：开发者模式
work：工作模式
-->
<environments default="development">
<environment id="development"> <transactionManager type="JDBC"/> <dataSource type="POOLED"> <property name="driver" value="com.mysql.jdbc.Driver"/> <property name="url" value="jdbc:mysql://127.0.0.1:3306/mybatis" /> <property name="username" value="root"/> <property name="password" value="root"/> </dataSource> </environment> </environments>
<!--导入实体类的映射文件-->
<mappers> <mapper resource="com/oracle/pojo/User.xml"/> </mappers></configuration>③实体类
package com.oracle.pojo;
public class User {
private int id;
private String userName; private String userAge; private String userAddress;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 getUserAge() {
return userAge; }public void setUserAge(String userAge) {
this.userAge = userAge; }public String getUserAddress() {
return userAddress; }public void setUserAddress(String userAddress) {
this.userAddress = userAddress; }@Override
public String toString() { return "User [id=" + id + ", userName=" + userName + ", userAge=" + userAge + ", userAddress=" + userAddress + "]"; }}
④实体类的配置文件User.xml
<?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="com.oracle.pojo.UserMapper">
<select id="selectUserByID" parameterType="int" resultType="User"> select * from user where id = #{id} </select></mapper>⑤测试类
package com.oracle.test;
import java.io.Reader;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;import org.apache.ibatis.session.SqlSessionFactory;import org.apache.ibatis.session.SqlSessionFactoryBuilder;import com.oracle.pojo.User;
public class Test {
private static SqlSessionFactory sqlSessionFactory; private static Reader reader;static{
try{ reader = Resources.getResourceAsReader("Configuration.xml"); sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader); }catch(Exception e){ e.printStackTrace(); } }public static SqlSessionFactory getSession(){
return sqlSessionFactory; } public static void main(String[] args) { SqlSession session = sqlSessionFactory.openSession(); try {//"com.oracle.pojo.UserMapper.selectUserByID"是根据实体类的配置文件写的，com.oracle.pojo.UserMapper是配置文件的namespace，selectUserByID是select的id
User user = (User) session.selectOne("com.oracle.pojo.UserMapper.selectUserByID", 1); System.out.println(user); } finally { session.close(); } }}
基于xml实现crud
1). 定义sql 映射xml 文件：
<insert id="insertUser" parameterType="com.atguigu.ibatis.bean.User">
insert into users(name, age) values(#{name}, #{age});</insert><delete id="deleteUser" parameterType="int">delete from users where id=#{id}</delete><update id="updateUser" parameterType="com.atguigu.ibatis.bean.User">update users set name=#{name},age=#{age} where id=#{id}</update><select id="selectUser" parameterType="int" resultType="com.atguigu.ibatis.bean.User">select * from users where id=#{id}</select><select id="selectAllUsers" resultType="com.atguigu.ibatis.bean.User">select * from users</select>2). 在config.xml 中注册这个映射文件
<mapper resource="net/lamp/java/ibatis/bean/userMapper.xml"/>3). 在dao 中调用：
/*//增
int count = session.insert("com.oracle.pojo.UserMapper.addUser", new User(-1,"kkk","12","nnnn")); System.out.println(count);*/ /*改 * int count = session.update("com.oracle.pojo.UserMapper.updateUser", new User(3, "kkk2222", "30", "mmmmmm")); System.out.println(count);*/ /*删 * session.delete("com.oracle.pojo.UserMapper.deleteUser", 3);*/ /*获取所有 * List<User> users = session.selectList("com.oracle.pojo.UserMapper.getAllUser"); System.out.println(users);*/ /*获取一个 * User user = (User) session.selectOne("com.oracle.pojo.UserMapper.selectUserByID", 1); System.out.println(user);*/基于注解实现crud
1). 定义sql 映射的接口
package com.oracle.pojo;
import java.util.List;
import org.apache.ibatis.annotations.Delete;
import org.apache.ibatis.annotations.Insert;import org.apache.ibatis.annotations.Select;import org.apache.ibatis.annotations.Update;public interface UserMapperImp {
@Insert("insert into user(userName,userAge,userAddress) values (#{userName},#{userAge},#{userAddress})") public int add(User user); @Delete("delete from user where id = #{id}") public void delete(int id); @Update("update user set userName=#{userName},userAge=#{userAge},userAddress=#{userAddress} where id=#{id}") public void update(User user); @Select("select * from user") public List<User> getAll(); @Select("select * from user where id = #{id}") public User getOne(int id);}2). 在config 中注册这个映射接口
<mapper class="com.atguigu.ibatis.crud.ano.UserMapperImp"/>
3). 在dao 类中调用
//--------基于注解---------
UserMapperImp mapper = session.getMapper(UserMapperImp.class); //mapper.add(new User(-1, "bb", "22", "cc")); //mapper.delete(4); //mapper.update(new User(5, "bbbb", "22", "cc")); /*List<User> users = mapper.getAll(); System.out.println(users);*/ User user = mapper.getOne(1); System.out.println(user);几个可以优化的地方
连接数据库的配置单独放在一个properties 文件中
在配置文件中
<properties resource="db.properties"/>
<property name="driver" value="${driver}" /><property name="url" value="${url}" /><property name="username" value="${username}" /><property name="password" value="${password}" />为实体类定义别名,简化sql 映射xml 文件中的引用
<typeAliases>
<typeAlias type="com.atguigu.ibatis.bean.User" alias="User"/></typeAliases>可以在src 下加入log4j 的配置文件,打印日志信息
1. 添加jar:
log4j-1.2.16.jar2.配置log4j.xml
<?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE log4j:configuration SYSTEM "log4j.dtd"><log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/"><appender name="STDOUT" class="org.apache.log4j.ConsoleAppender"><layout class="org.apache.log4j.PatternLayout"><param name="ConversionPattern"value="%-5p %d{MM-dd HH:mm:ss,SSS} %m (%F:%L) \n" /></layout></appender><logger name="java.sql"><level value="debug" /></logger><logger name="org.apache.ibatis"><level value="debug" /></logger><root><level value="debug" /><appender-ref ref="STDOUT" /></root></log4j:configuration>