首先，先补充几个简单的笔记-----定义别名
前两天的笔记里代码还是存在一定的问题，问题在于：
使用statementID的方式存在如下问题
1.传入的statement字符串有可能会写错,写错的时候必须等到运行的时候才发现
2.传入的参数无法限定类型.
解决办法在于
使用Mapper接口的方式:
1.新建UserMapper接口：
（1）接口的全限定名==UserMapper.xml中的namespace
（2）接口中方法==UserMapper.xml中标签ID
（3）接口方法上的参数==UserMapper.xml中的parameterType
（4）接口方法上的返回值类型==UserMapper.xml中的resultType
对应的API
UserMapper mapper = session.getMapper(UserMapper.class);
文件目录结构
mybatis.xml文件的编写
<?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>
<properties resource="db.properties"></properties> //引入db.properties文件的第二种方式（个人喜欢第二种方式，原因简单方便）
<typeAliases>
<typeAlias type="mybatis.domain.user" alias="user" ></typeAlias> //使用别名
</typeAliases>
<environments default="default">
<environment id="default">
<transactionManager type="JDBC"></transactionManager>
<dataSource type="POOLED">
<property name="driver" value="${db.driverClassName}"></property>
<property name="url" value="${db.url}"></property>
<property name="username" value="${db.username}"></property>
<property name="password" value="${db.password}"></property>
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="mybatis/domain/usermapper.xml"></mapper>
</mappers>
</configuration>
usermapper.xml文件的编写
<?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="mybatis.domain.usermapper">
<insert id="save" parameterType="user" keyColumn="id" keyProperty="id" useGeneratedKeys="true">
INSERT INTO user (username,password,age)VALUES (#{username},#{password},#{age})
</insert>
<update id="update" parameterType="user">
UPDATE user SET username=#{username},password=#{password},age=#{age} WHERE id=#{id}
</update>
<select id="search" parameterType="long" resultType="user">
SELECT *FROM user WHERE id=#{id}
</select>
<select id="list" resultType="user">
SELECT *FROM user
</select>
<delete id="delete" parameterType="long">
DELETE FROM user WHERE id=#{id}
</delete>
</mapper>
log4j.properties文件的编写（文件名log4j.properties千万不能错）
# Global logging configuration
log4j.rootLogger=ERROR, stdout
# MyBatis logging configuration...
log4j.logger.mybatis.domain.usermapper=TRACE
# Console output...
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n
db.properties文件的编写
db.driverClassName=com.mysql.jdbc.Driver
db.url=jdbc:mysql://localhost:3306/mybatis
db.username=root
db.password=123456
user类的编写
package mybatis.domain;
import lombok.Data;
public class user {
private Long id;
private String username;
private String password;
private Integer age;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
@Override
public String toString() {
return "user{" +
"id=" + id +
", username='" + username + '\'' +
", password='" + password + '\'' +
", age=" + age +
'}';
}
}
mybatisutils工具类的编写
package mybatis.utils;
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 java.io.IOException;
public class mybatisutils {
private SqlSessionFactory sf;
private static mybatisutils instance=new mybatisutils();
public mybatisutils(){
try {
sf=new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis.xml"));
} catch (IOException e) {
e.printStackTrace();
}
}
public static SqlSession opensession(){
return instance.sf.openSession();
}
}
usermapper接口的编写
package mybatis.domain;
import java.util.List;
public interface usermapper {
void save(user u);
void update(user u);
user search(Long id);
List<user>list();
void delete(Long id);
}
usertest测试方法
package mybatis.test;
import mybatis.domain.user;
import mybatis.domain.usermapper;
import mybatis.utils.mybatisutils;
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 org.junit.Test;
import java.io.IOException;
import java.util.List;
public class usertest {
@Test
public void test() throws IOException {
user u=new user();
u.setAge(17);
u.setUsername("小李子");
u.setPassword("123456");
SqlSessionFactory sf=new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis.xml"));
SqlSession session=mybatisutils.opensession();
//session.insert("mybatis.domain.usermapper.save",u);
usermapper mapper=session.getMapper(usermapper.class);
mapper.save(u);
session.close();
System.out.println(u);
}
@Test
public void testupdate(){
user u=new user();
u.setAge(47);
u.setUsername("李公公");
u.setPassword("123");
u.setId(4L);
SqlSession session=mybatisutils.opensession();
//session.update("mybatis.domain.usermapper.update",u);
usermapper mapper=session.getMapper(usermapper.class);
mapper.update(u);
session.close();
}
@Test
public void testget(){
SqlSession session=mybatisutils.opensession();
//user u=session.selectOne("mybatis.domain.usermapper.search",1L);
usermapper mapper=session.getMapper(usermapper.class);
user u=mapper.search(4L);
System.out.println(u);
session.close();
}
@Test
public void testlist(){
SqlSession session=mybatisutils.opensession();
//List<user>users=session.selectList("mybatis.domain.usermapper.list");
//for (user user : users) {
// System.out.println(user);
//}
usermapper mapper=session.getMapper(usermapper.class);
List<user>list=mapper.list();
for (user user : list) {
System.out.println(user);
}
session.close();
}
@Test
public void testdelete(){
SqlSession session=mybatisutils.opensession();
//session.delete("mybatis.domain.usermapper.delete",7L);
usermapper mapper=session.getMapper(usermapper.class);
mapper.delete(12L);
session.close();
}
}
测试结果
反编译结果如图
