大数据正式35

大数据正式35

MyBatis

JDBC缺点

需要频繁开闭数据库

查询结果需要人为进行封装

JDBC没有缓存

Sql写在java文件

MyBatis优点

内置数据库连接池

自动封装数据

有缓存

Sql写在配置文件中

流程

入门实例

显示user

目录结构



依赖jart包



代码

com.peng.pojo

User

package com.peng.pojo; public class User { private int id; private String name; private int age;

public User() {
super();
}

public User(int id, String name, int age) {
super();
this.id = id;
this.name = name;
this.age = age;
}

public int getId() {
return id;
}

public void setId(int id) {
this.id = id;
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public int getAge() {
return age;
}

public void setAge(int age) {
this.age = age;
}

@Override
public String toString() {
return "编号：" + id + "，姓名：" + name + "，年龄：" + age;
}

}

UserMapper

<?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="UserMapper">
<select id="findAll" resultType="com.peng.pojoUser">select * from user</select>
</mapper>

com.peng.test

Test

package com.peng.test;

import java.io.InputStream;
import java.util.List;

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.peng.pojo.User;

public class Test {
@org.junit.Test
public void findAllTest() throws Exception {
// 加载配置文件
InputStream in = Resources.getResourceAsStream("sqlMapConfig.xml");
// 创建会话工厂
SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in);
// 创建会话对象
SqlSession openSession = factory.openSession();
// 执行SQL
List<User> selectList = openSession.selectList("UserMapper.findAll");
for (User user : selectList) {
System.out.println(user);
}
}
}

src下的配置文件

sqlMapConfig.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>
<!-- 配置数据源 -->
<environments default="mysql">
<environment id="mysql">
<transactionManager type="JDBC" />
<dataSource type="POOLED">

<property name="driver" value="com.mysql.jdbc.Driver" />
<property name="url"
value="jdbc:mysql://localhost:3306/mybatis_db?characterEncoding=utf-8" />
<property name="username" value="root" />
<property name="password" value="root" />
</dataSource>
</environment>

<environment id="oracle">
<transactionManager type="JDBC" />
<dataSource type="POOLED">
<property name="driver" value="oracle.jdbc.driver.OracleDriver" />
<property name="url" value="jdbc:oracle:thin:@127.0.0.1:1521:XE" />
<property name="username" value="ht1602" />
<property name="password" value="htdb" />
</dataSource>
</environment>
</environments>

<!-- 映射文件 -->
<mappers>
<mapper resource="com/peng/pojo/UserMapper.xml" />
</mappers>

</configuration>

log4j.properties

log4j.rootLogger=DEBUG, Console
#Console
log4j.appender.Console=org.apache.log4j.ConsoleAppender
log4j.appender.Console.layout=org.apache.log4j.PatternLayout
log4j.appender.Console.layout.ConversionPattern=%d [%t] %-5p [%c] - %m%n
log4j.logger.java.sql.ResultSet=INFO
log4j.logger.org.apache=INFO
log4j.logger.java.sql.Connection=DEBUG
log4j.logger.java.sql.Statement=DEBUG
log4j.logger.java.sql.PreparedStatement=DEBUG

130df

注：

openSession（true）：每一次sql都提交

取值符号

#{id}会自动加引号--有有预编译效果（防止sql注入）

${id}不加引号

不加引号的地方----order by 属性名

单值传递和多值传递

单值：可以写任意参数代表传的参数

多值：和原参数一致

复用

<?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="UserMapper">
<sql id="selectUser">select * from user</sql>
<select id="findAll" resultType="User">
<include refid="selectUser"></include>
</select>
</mapper>

包的别名

<!-- 别名 -->
<typeAliases>
<typeAlias type="com.peng.pojo.User" alias="User" />
</typeAliases>

动态更新

普通

<update id="updateByID">
update user set name=#{name},age=#{age}
</update>

set标签--去掉多余逗号

例子

<update id="updateByID">
update user
<set>
<if test="name!=null">name=#{name},</if>
<if test="age!=null">age=#{age},</if>
</set>
</update>

动态查询

普通

<sql id="selectUser">select * from user</sql>
<select id="findAll" resultType="User">
<include refid="selectUser"></include>
where name=#{name} and age=#{age}
</select>

where--去掉多余的and

动态

<sql id="selectUser">select * from user</sql>
<select id="findAll" resultType="User">
<include refid="selectUser"></include>
<where>
<if test="name!=null">and name=#{name}</if>
<if test="age!=null">and age=#{age}</if>
</where>
</select>

注：and放前面；逗号放后面

动态插入

<!-- 动态插入 -->
<insert id="insertBy">
insert into user
<trim prefix="(" suffix=")" suffixOverrides=","><!--去掉多余逗号 -->
<if test="name!=null">name,</if>
<if test="age!=null">age,</if>
</trim>
</insert>
</mapper>

批量删除之数组形式

UserMapper

<!-- 批量删除：数组 -->
<delete id="deleteSome">
delete from user where id in
<foreach collection="array" open="(" close=")" separator=","<!-- 拼接-->
item="id">#{id}
</foreach>
</delete>

Test

// 通过id数组来批量删除
@org.junit.Test
public void DeleteSomeTest() {
int[] ids = { 2, 3, 4 };
openSession.delete("UserMapper.deleteSome_array", ids);
}

批量删除之List形式

UserMapper

<!-- 批量删除：集合 -->
<delete id="deleteSome_list">
delete from user where id in
<foreach collection="list" open="(" close=")" separator=","
item="user">#{user.id}</foreach>
</delete>

Test

// 通过集合来批量删除
@org.junit.Test
public void DeleteSomeTest2() {
List<User> user_list = new ArrayList<User>();
// 创建数据
for (int i = 1; i < 8; i++) {
user_list.add(new User(i, "a" + i, i));
}
openSession.delete("UserMapper.deleteSome_list", user_list);
}

补充