mybatis基本使用

1,建库建表

SQL脚本

CREATE TABLE `user`  (`id` bigint(20) NOT NULL AUTO_INCREMENT,`username` varchar(30) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,`password` varchar(30) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,`age` int(11) NULL DEFAULT NULL,`gender` varchar(6) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,`addr` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 11 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = COMPACT;INSERT INTO `user` VALUES (1, 'zhangsan', '123', 20, 'male', 'qd');
INSERT INTO `user` VALUES (2, 'lisi', '123', 21, 'male', 'bj');
INSERT INTO `user` VALUES (4, 'tom', '123', 19, 'male', 'nj');
INSERT INTO `user` VALUES (5, 'wangwu', '123', 20, 'male', 'sh');
INSERT INTO `user` VALUES (6, 'weihua', '111', 21, 'female', 'sz');

2，新建maven项目，导入相关jar包，配置java目录下的xml文件为资源文件，让Maven能够识别，从而进行编译。

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<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/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><groupId>org.example</groupId><artifactId>mybatis02</artifactId><version>1.0-SNAPSHOT</version><properties><maven.compiler.source>8</maven.compiler.source><maven.compiler.target>8</maven.compiler.target></properties><dependencies><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>5.1.47</version></dependency><dependency><groupId>org.mybatis</groupId><artifactId>mybatis</artifactId><version>3.4.6</version></dependency><dependency><!-- 测试 test --><groupId>junit</groupId><artifactId>junit</artifactId><version>4.13</version><!--只在测试时有效，包括测试代码的编译，执行。--><scope>test</scope></dependency><dependency><!-- log for java --><groupId>log4j</groupId><artifactId>log4j</artifactId><version>1.2.17</version></dependency></dependencies><!--  配置java目录下的xml文件为资源文件，让Maven能够识别，从而进行编译。 --><build><resources><resource><directory>src/main/java</directory><includes><include>**/*.xml</include></includes></resource></resources></build></project>

3，创建实体类

创建表示用户的实体类User

package com.bean;
public class User {private Long id;private String username;private String password;private Integer age;private String gender;private String addr;//set、get//toString
}

4，编写日志配置文件

log4j.properties

#
# Hibernate, Relational Persistence for Idiomatic Java
#
# License: GNU Lesser General Public License (LGPL), version 2.1 or later.
# See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
#### direct log messages to stdout ###
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target=System.err
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{1}:%L - %m%n### direct messages to file hibernate.log ###
#log4j.appender.file=org.apache.log4j.FileAppender
#log4j.appender.file.File=hibernate.log
#log4j.appender.file.layout=org.apache.log4j.PatternLayout
#log4j.appender.file.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{1}:%L - %m%n### set log levels - for more verbose logging change 'info' to 'debug' ###log4j.rootLogger=debug, stdout

这个文件编写不需要掌握，用的时候直接拷贝即可。

4，编写UserMapper接口

接口的名字我们一般命名为XxxMapper，所在的包命名为xxx.xxx.mapper，这是一种习惯。

当然也可以命名为XxxDao。

package com.mapper;
public interface UserMapper {List<User> findAll();
}

5，编写映射文件（UserMapper.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.mapper.UserMapper"><select id="findAll" resultType="com.bean.User">SELECT * FROM user</select>
</mapper>

6，编写核心配置文件SqlMapConfig.xml

该文件在resources目录下

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configurationPUBLIC "-//mybatis.org//DTD Config 3.0//EN""http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration><!-- 配置别名 --><typeAliases><!--     <package name="com.bean"/>--><typeAlias type="com.bean.User" alias="user"/></typeAliases><!-- 配置环境 --><environments default="dev"><environment id="dev"><transactionManager type="JDBC"></transactionManager><dataSource type="POOLED"><property name="driver" value="com.mysql.jdbc.Driver"/><property name="url"value="jdbc:mysql://localhost:3306/db_test_mybatis?useSSL=false&amp;jdbc:mysql://localhost:3306/test?useSSL=false&amp;useUnicode=true&amp;characterEncoding=utf8"/><property name="username" value="root"/><property name="password" value="root"/></dataSource></environment></environments><!--加载映射文件，如果不添加  Type interface com.mapper.UserMapper is not known to the MapperRegistry. MapperRegistry不知道接口类型com.mapper.UserMapper。 --><mappers><package name="com.mapper"/><!--        <mapper resource="com/mapper/UserMapper.xml" />--></mappers></configuration>

7，编写测试类

public class MyTest {private SqlSession sqlSession;private UserMapper userMapper;@Beforepublic void init() throws IOException {//加载核心配置文件InputStream resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");//创建SqlSessionFactorySqlSessionFactory factory = new SqlSessionFactoryBuilder().build(resourceAsStream);//获取连接sqlSession = factory.openSession();//创建接口的代理对象userMapper = sqlSession.getMapper(UserMapper.class);}@Afterpublic void destroy() {//关闭连接sqlSession.close();}@Testpublic void testFindById() {User user = userMapper.findById(1);System.out.println(user);}@Testpublic void testFindAll() {List<User> users = userMapper.findAll();users.forEach(user -> System.out.println(user));}
}

运行测试方法，进行测试。