MyBatis快速入門(mén)(簡(jiǎn)明淺析易懂)

更新時(shí)間：2016年11月08日 10:05:03 作者：夏中偉

MyBatis是支持普通SQL查詢，存儲(chǔ)過(guò)程和高級(jí)映射的優(yōu)秀持久層框架。mybatis的學(xué)習(xí)是程序員的必修課。今天小編通過(guò)分享本教程幫助大家快速入門(mén)mybatis，對(duì)mybatis入門(mén)知識(shí)感興趣的朋友參考下吧

一、MyBatis簡(jiǎn)介

MyBatis是支持普通SQL查詢，存儲(chǔ)過(guò)程和高級(jí)映射的優(yōu)秀持久層框架。

MyBatis消除了幾乎所有的JDBC代碼和參數(shù)的手工設(shè)置以及對(duì)結(jié)果集的檢索封裝。

MyBatis可以使用簡(jiǎn)單的XML或注解用于配置和原始映射，將接口和Java的POJO（Plain Old Java Objects，普通的Java對(duì)象）映射成數(shù)據(jù)庫(kù)中的記錄.

JDBC -> dbutils(自動(dòng)封裝) -> MyBatis -> Hibernate

mybatis是將sql寫(xiě)在xml中，然后去訪問(wèn)數(shù)據(jù)庫(kù)。

二、MyBatis快速入門(mén)

2.1.新建java項(xiàng)目

　　添加mybatis和mysql的驅(qū)動(dòng)jar：mybatis-3.1.1.jar,mysql-connector-java-5.1.7-bin.jar

2.2.新建表

create database mybatis;
use mybatis;
create table users(id int primary key auto_increment, name varchar(20), age int);
insert into users (name,age) values('Tom',12);
insert into users (name, age) values('Jack',11);

2.3.添加mybatis的配置文件conf.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>
<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://localhost:3306/mybatis" />
<property name="username" value="root" />
<property name="password" value="root" />
</dataSource>
</environment>
</environments>
</configuration>

2.4.定義表對(duì)應(yīng)的實(shí)體類

public class User {
private int id;
private String name;
private int age;
//get,set方法
}

2.5.定義操作users表的sql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.atguigu.mybatis_test.test1.userMapper">
<select id="getUser" parameterType="int"
resultType="com.atguigu.mybatis_test.test1.User">
select * from users where id=#{id}
</select>
</mapper>

2.6.在conf.xml文件中注冊(cè)u(píng)serMapper.xml文件

<mappers>
<mapper resource="com/atguigu/mybatis_test/test1/userMapper.xml"/>
</mappers>

2.7.編寫(xiě)測(cè)試代碼：執(zhí)行定義的select語(yǔ)句

public class Test {
public static void main(String[] args) throws IOException {
String resource = "conf.xml";
//加載mybatis的配置文件（它也加載關(guān)聯(lián)的映射文件）
Reader reader = Resources.getResourceAsReader(resource);
//構(gòu)建sqlSession的工廠
SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader);
//創(chuàng)建能執(zhí)行映射文件中sql的sqlSession
SqlSession session = sessionFactory.openSession();
//映射sql的標(biāo)識(shí)字符串
String statement = "com.atguigu.mybatis.bean.userMapper"+".selectUser";
//執(zhí)行查詢返回一個(gè)唯一user對(duì)象的sql
User user = session.selectOne(statement, 1);
System.out.println(user);
}
}

三、操作users表的CRUD

3.1.xml的實(shí)現(xiàn)

3.1.1.定義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>

3.1.2.在config.xml中注冊(cè)這個(gè)映射文件

<mapper resource=" com/atguigu/ibatis/bean/userMapper.xml"/>

3.1.3.在dao中調(diào)用

public User getUserById(int id) {
SqlSession session = sessionFactory.openSession();
User user = session.selectOne(URI+".selectUser", id);
return user;
}

3.2.注解的實(shí)現(xiàn)

3.2.1.定義sql映射的接口

public interface UserMapper {
@Insert("insert into users(name, age) values(#{name}, #{age})")
public int insertUser(User user);
@Delete("delete from users where id=#{id}")
public int deleteUserById(int id);
@Update("update users set name=#{name},age=#{age} where id=#{id}")
public int updateUser(User user);
@Select("select * from users where id=#{id}")
public User getUserById(int id);
@Select("select * from users")
public List<User> getAllUser();
}

3.2.2.在config中注冊(cè)這個(gè)映射接口

<mapper class="com.atguigu.ibatis.crud.ano.UserMapper"/>

3.2.3.在dao中調(diào)用

public User getUserById(int id) {
SqlSession session = sessionFactory.openSession();
UserMapper mapper = session.getMapper(UserMapper.class);
User user = mapper.getUserById(id);
return user;
}

四、幾個(gè)可以優(yōu)化的地方

4.1.連接數(shù)據(jù)庫(kù)的配置可以單獨(dú)放在一個(gè)properties文件中。

## db.properties<br>
<properties resource="db.properties"/>
<property name="driver" value="${driver}" />
<property name="url" value="${url}" />
<property name="username" value="${username}" />
<property name="password" value="${password}" />

4.2.為實(shí)體類定義別名,簡(jiǎn)化sql映射xml文件中的引用

<typeAliases>
<typeAlias type="com.atguigu.ibatis.bean.User" alias="_User"/>
</typeAliases>

4.3.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.jar

2.1. log4j.properties(方式一)

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

2.2. log4j.xml(方式二)

<?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>

五、解決字段名與實(shí)體類屬性名不相同的沖突

5.1.準(zhǔn)備表和字段

CREATE TABLE orders(
order_id INT PRIMARY KEY AUTO_INCREMENT,
order_no VARCHAR(20),
order_price FLOAT
);
INSERT INTO orders(order_no, order_price) VALUES('aaaa', 23);
INSERT INTO orders(order_no, order_price) VALUES('bbbb', 33);
INSERT INTO orders(order_no, order_price) VALUES('cccc', 22);

5.2.定義實(shí)體類

public class Order {
private int id;
private String orderNo;
private float price;
}

5.3.實(shí)現(xiàn)getOrderById(id)的查詢：

方式一: 通過(guò)在sql語(yǔ)句中定義別名

<select id="selectOrder" parameterType="int" resultType="_Order">
select order_id id, order_no orderNo,order_price price from orders where order_id=#{id}
</select>

方式二: 通過(guò)<resultMap>

<select id="selectOrderResultMap" parameterType="int" resultMap="orderResultMap">
select * from orders where order_id=#{id}
</select>
<resultMap type="_Order" id="orderResultMap">
<id property="id" column="order_id"/>
<result property="orderNo" column="order_no"/>
<result property="price" column="order_price"/>
</resultMap>

六、實(shí)現(xiàn)關(guān)聯(lián)表查詢

6.1.一對(duì)一關(guān)聯(lián)

6.1.1.提出需求

根據(jù)班級(jí)id查詢班級(jí)信息(帶老師的信息)

6.1.2.創(chuàng)建表和數(shù)據(jù)

CREATE TABLE teacher(
t_id INT PRIMARY KEY AUTO_INCREMENT,
t_name VARCHAR(20)
);
CREATE TABLE class(
c_id INT PRIMARY KEY AUTO_INCREMENT,
c_name VARCHAR(20),
teacher_id INT
);
ALTER TABLE class ADD CONSTRAINT fk_teacher_id FOREIGN KEY (teacher_id) REFERENCES teacher(t_id); 
INSERT INTO teacher(t_name) VALUES('LS1');
INSERT INTO teacher(t_name) VALUES('LS2');
INSERT INTO class(c_name, teacher_id) VALUES('bj_a', 1);
INSERT INTO class(c_name, teacher_id) VALUES('bj_b', 2);

6.1.3.定義實(shí)體類：

public class Teacher {
private int id;
private String name;
}
public class Classes {
private int id;
private String name;
private Teacher teacher;
}

6.1.4.定義sql映射文件ClassMapper.xml

<!--
方式一: 嵌套結(jié)果: 使用嵌套結(jié)果映射來(lái)處理重復(fù)的聯(lián)合結(jié)果的子集
SELECT * FROM class c, teacher t,student s WHERE c.teacher_id=t.t_id AND c.C_id=s.class_id AND c.c_id=1
-->
<select id="getClass3" parameterType="int" resultMap="ClassResultMap3">
select * from class c, teacher t,student s where c.teacher_id=t.t_id and c.C_id=s.class_id and c.c_id=#{id}
</select>
<resultMap type="_Classes" id="ClassResultMap3">
<id property="id" column="c_id"/>
<result property="name" column="c_name"/>
<association property="teacher" column="teacher_id" javaType="_Teacher">
<id property="id" column="t_id"/>
<result property="name" column="t_name"/>
</association>
<!-- ofType指定students集合中的對(duì)象類型 -->
<collection property="students" ofType="_Student">
<id property="id" column="s_id"/>
<result property="name" column="s_name"/>
</collection>
</resultMap>
<!--
方式二：嵌套查詢：通過(guò)執(zhí)行另外一個(gè)SQL映射語(yǔ)句來(lái)返回預(yù)期的復(fù)雜類型
SELECT * FROM class WHERE c_id=1;
SELECT * FROM teacher WHERE t_id=1 //1 是上一個(gè)查詢得到的teacher_id的值
SELECT * FROM student WHERE class_id=1 //1是第一個(gè)查詢得到的c_id字段的值
-->
<select id="getClass4" parameterType="int" resultMap="ClassResultMap4">
select * from class where c_id=#{id}
</select>
<resultMap type="_Classes" id="ClassResultMap4">
<id property="id" column="c_id"/>
<result property="name" column="c_name"/>
<association property="teacher" column="teacher_id" javaType="_Teacher" select="getTeacher2"></association>
<collection property="students" ofType="_Student" column="c_id" select="getStudent"></collection>
</resultMap>
<select id="getTeacher2" parameterType="int" resultType="_Teacher">
SELECT t_id id, t_name name FROM teacher WHERE t_id=#{id}
</select>
<select id="getStudent" parameterType="int" resultType="_Student">
SELECT s_id id, s_name name FROM student WHERE class_id=#{id}
</select>

6.1.5.測(cè)試

@Test
public void testOO() {
SqlSession sqlSession = factory.openSession();
Classes c = sqlSession.selectOne("com.atguigu.day03_mybatis.test5.OOMapper.getClass", 1);
System.out.println(c);
}
@Test
public void testOO2() {
SqlSession sqlSession = factory.openSession();
Classes c = sqlSession.selectOne("com.atguigu.day03_mybatis.test5.OOMapper.getClass2", 1);
System.out.println(c);
}

6.2.一對(duì)多關(guān)聯(lián)

6.2.1.提出需求

根據(jù)classId查詢對(duì)應(yīng)的班級(jí)信息,包括學(xué)生,老師

6.2.2.創(chuàng)建表和數(shù)據(jù)：

CREATE TABLE student(
s_id INT PRIMARY KEY AUTO_INCREMENT,
s_name VARCHAR(20),
class_id INT
);
INSERT INTO student(s_name, class_id) VALUES('xs_A', 1);
INSERT INTO student(s_name, class_id) VALUES('xs_B', 1);
INSERT INTO student(s_name, class_id) VALUES('xs_C', 1);
INSERT INTO student(s_name, class_id) VALUES('xs_D', 2);
INSERT INTO student(s_name, class_id) VALUES('xs_E', 2);
INSERT INTO student(s_name, class_id) VALUES('xs_F', 2);

6.2.3.定義實(shí)體類

public class Student {
private int id;
private String name;
}
public class Classes {
private int id;
private String name;
private Teacher teacher;
private List<Student> students;
}

6.2.4.定義sql映射文件ClassMapper.xml

<!--
方式一: 嵌套結(jié)果: 使用嵌套結(jié)果映射來(lái)處理重復(fù)的聯(lián)合結(jié)果的子集
SELECT * FROM class c, teacher t,student s WHERE c.teacher_id=t.t_id AND c.C_id=s.class_id AND c.c_id=1
-->
<select id="getClass3" parameterType="int" resultMap="ClassResultMap3">
select * from class c, teacher t,student s where c.teacher_id=t.t_id and c.C_id=s.class_id and c.c_id=#{id}
</select>
<resultMap type="_Classes" id="ClassResultMap3">
<id property="id" column="c_id"/>
<result property="name" column="c_name"/>
<association property="teacher" column="teacher_id" javaType="_Teacher">
<id property="id" column="t_id"/>
<result property="name" column="t_name"/>
</association>
<!-- ofType指定students集合中的對(duì)象類型 -->
<collection property="students" ofType="_Student">
<id property="id" column="s_id"/>
<result property="name" column="s_name"/>
</collection>
</resultMap>
<!--
方式二：嵌套查詢：通過(guò)執(zhí)行另外一個(gè)SQL映射語(yǔ)句來(lái)返回預(yù)期的復(fù)雜類型
SELECT * FROM class WHERE c_id=1;
SELECT * FROM teacher WHERE t_id=1 //1 是上一個(gè)查詢得到的teacher_id的值
SELECT * FROM student WHERE class_id=1 //1是第一個(gè)查詢得到的c_id字段的值
-->
<select id="getClass4" parameterType="int" resultMap="ClassResultMap4">
select * from class where c_id=#{id}
</select>
<resultMap type="_Classes" id="ClassResultMap4">
<id property="id" column="c_id"/>
<result property="name" column="c_name"/>
<association property="teacher" column="teacher_id" javaType="_Teacher" select="getTeacher2"></association>
<collection property="students" ofType="_Student" column="c_id" select="getStudent"></collection>
</resultMap>
<select id="getTeacher2" parameterType="int" resultType="_Teacher">
SELECT t_id id, t_name name FROM teacher WHERE t_id=#{id}
</select>
<select id="getStudent" parameterType="int" resultType="_Student">
SELECT s_id id, s_name name FROM student WHERE class_id=#{id}
</select>

6.2.5.測(cè)試

@Test
public void testOM() {
SqlSession sqlSession = factory.openSession();
Classes c = sqlSession.selectOne("com.atguigu.day03_mybatis.test5.OOMapper.getClass3", 1);
System.out.println(c);
}
@Test
public void testOM2() {
SqlSession sqlSession = factory.openSession();
Classes c = sqlSession.selectOne("com.atguigu.day03_mybatis.test5.OOMapper.getClass4", 1);
System.out.println(c);
}

七、動(dòng)態(tài)sql與模糊查詢

7.1.需求

實(shí)現(xiàn)多條件查詢用戶(姓名模糊匹配, 年齡在指定的最小值到最大值之間)。

7.2.準(zhǔn)備數(shù)據(jù)庫(kù)和表

create table d_user( 
id int primary key auto_increment, 
name varchar(10),
age int(3)
);
insert into d_user(name,age) values('Tom',12); 
insert into d_user(name,age) values('Bob',13); 
insert into d_user(name,age) values('Jack',18);
7.3.ConditionUser(查詢條件實(shí)體類)
private String name;
private int minAge;
private int maxAge;

7.4.User表實(shí)體類

private int id;
private String name;
private int age;

7.5.userMapper.xml(映射文件)

<?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.atguigu.day03_mybatis.test6.userMapper">
<select id="getUser" parameterType="com.atguigu.day03_mybatis.test6.ConditionUser" resultType="com.atguigu.day03_mybatis.test6.User">
select * from d_user where age>=#{minAge} and age<=#{maxAge}
<if test='name!="%null%"'>and name like #{name}</if>
</select>
</mapper>

7.6.UserTest(測(cè)試)

public class UserTest {
public static void main(String[] args) throws IOException {
Reader reader = Resources.getResourceAsReader("conf.xml");
SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader);
SqlSession sqlSession = sessionFactory.openSession();
String statement = "com.atguigu.day03_mybatis.test6.userMapper.getUser";
List<User> list = sqlSession.selectList(statement, new ConditionUser("%a%", 1, 12));
System.out.println(list);
}
}

MyBatis中可用的動(dòng)態(tài)SQL標(biāo)簽

八、調(diào)用存儲(chǔ)過(guò)程

8.1.提出需求

查詢得到男性或女性的數(shù)量, 如果傳入的是0就女性否則是男性

8.2.準(zhǔn)備數(shù)據(jù)庫(kù)表和存儲(chǔ)過(guò)程:

create table p_user( 
id int primary key auto_increment, 
name varchar(10),
sex char(2)
);
insert into p_user(name,sex) values('A',"男"); 
insert into p_user(name,sex) values('B',"女"); 
insert into p_user(name,sex) values('C',"男"); 
#創(chuàng)建存儲(chǔ)過(guò)程(查詢得到男性或女性的數(shù)量, 如果傳入的是0就女性否則是男性)
DELIMITER $
CREATE PROCEDURE mybatis.ges_user_count(IN sex_id INT, OUT user_count INT)
BEGIN 
IF sex_id=0 THEN
SELECT COUNT(*) FROM mybatis.p_user WHERE p_user.sex='女' INTO user_count;
ELSE
SELECT COUNT(*) FROM mybatis.p_user WHERE p_user.sex='男' INTO user_count;
END IF;
END
$
#調(diào)用存儲(chǔ)過(guò)程
DELIMITER ;
SET @user_count = 0;
CALL mybatis.ges_user_count(1, @user_count);
SELECT @user_count;

8.3.創(chuàng)建表的實(shí)體類

public class User {
private String id;
private String name;
private String sex;
}

8.4.userMapper.xml

<mapper namespace="com.atguigu.mybatis.test7.userMapper">
<!--
查詢得到男性或女性的數(shù)量, 如果傳入的是0就女性否則是男性
CALL mybatis.get_user_count(1, @user_count);
-->
<select id="getCount" statementType="CALLABLE" parameterMap="getCountMap">
call mybatis.get_user_count(?,?)
</select>
<parameterMap type="java.util.Map" id="getCountMap">
<parameter property="sex_id" mode="IN" jdbcType="INTEGER"/>
<parameter property="user_count" mode="OUT" jdbcType="INTEGER"/>
</parameterMap>
</mapper>

8.5.測(cè)試

Map<String, Integer> paramMap = new HashMap<>();
paramMap.put("sex_id", 0);
session.selectOne(statement, paramMap);
Integer userCount = paramMap.get("user_count");
System.out.println(userCount);

九、MyBatis緩存

9.1.理解mybatis緩存

正如大多數(shù)持久層框架一樣，MyBatis 同樣提供了一級(jí)緩存和二級(jí)緩存的支持

1.一級(jí)緩存: 基于PerpetualCache 的 HashMap本地緩存，其存儲(chǔ)作用域?yàn)?Session，當(dāng) Session flush 或 close 之后，該Session中的所有 Cache 就將清空。

2. 二級(jí)緩存與一級(jí)緩存其機(jī)制相同，默認(rèn)也是采用 PerpetualCache，HashMap存儲(chǔ)，不同在于其存儲(chǔ)作用域?yàn)?Mapper(Namespace)，并且可自定義存儲(chǔ)源，如 Ehcache。

3. 對(duì)于緩存數(shù)據(jù)更新機(jī)制，當(dāng)某一個(gè)作用域(一級(jí)緩存Session/二級(jí)緩存Namespaces)的進(jìn)行了 C/U/D 操作后，默認(rèn)該作用域下所有 select 中的緩存將被clear。

9.2.mybatis一級(jí)緩存

9.2.1.根據(jù)任務(wù)查詢

根據(jù)id查詢對(duì)應(yīng)的用戶記錄對(duì)象。

9.2.2.準(zhǔn)備數(shù)據(jù)庫(kù)表和數(shù)據(jù)

CREATE TABLE c_user(
id INT PRIMARY KEY AUTO_INCREMENT,
NAME VARCHAR(20),
age INT
);
INSERT INTO c_user(NAME, age) VALUES('Tom', 12);
INSERT INTO c_user(NAME, age) VALUES('Jack', 11);

9.2.3.創(chuàng)建表的實(shí)體類

public class User implements Serializable{
private int id;
private String name;
private int age;

9.2.4.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.atguigu.mybatis.test8.userMapper">
<select id="getUser" parameterType="int" resultType="_CUser">
select * from c_user where id=#{id}
</select>
<update id="updateUser" parameterType="_CUser">
update c_user set
name=#{name}, age=#{age} where id=#{id}
</update>
</mapper>

9.2.5.測(cè)試

/*
* 一級(jí)緩存: 也就Session級(jí)的緩存(默認(rèn)開(kāi)啟)
*/
@Test
public void testCache1() {
SqlSession session = MybatisUtils.getSession();
String statement = "com.atguigu.mybatis.test8.userMapper.getUser";
User user = session.selectOne(statement, 1);
System.out.println(user);
/*
* 一級(jí)緩存默認(rèn)就會(huì)被使用
*/
/*
user = session.selectOne(statement, 1);
System.out.println(user);
*/
/*
1. 必須是同一個(gè)Session,如果session對(duì)象已經(jīng)close()過(guò)了就不可能用了
*/
/*
session = MybatisUtils.getSession();
user = session.selectOne(statement, 1);
System.out.println(user);
*/
/*
2. 查詢條件是一樣的
*/
/*
user = session.selectOne(statement, 2);
System.out.println(user);
*/
/*
3. 沒(méi)有執(zhí)行過(guò)session.clearCache()清理緩存
*/
/*
session.clearCache();
user = session.selectOne(statement, 2);
System.out.println(user);
*/
/*
4. 沒(méi)有執(zhí)行過(guò)增刪改的操作(這些操作都會(huì)清理緩存)
*/
/*
session.update("com.atguigu.mybatis.test8.userMapper.updateUser",
new User(2, "user", 23));
user = session.selectOne(statement, 2);
System.out.println(user);
*/
}

9.3.MyBatis二級(jí)緩存

9.3.1.添加一個(gè)<cache>在userMapper.xml中

<mapper namespace="com.atguigu.mybatis.test8.userMapper">
<cache/>

9.3.2.測(cè)試

/*
* 測(cè)試二級(jí)緩存
*/
@Test
public void testCache2() {
String statement = "com.atguigu.mybatis.test8.userMapper.getUser";
SqlSession session = MybatisUtils.getSession();
User user = session.selectOne(statement, 1);
session.commit();
System.out.println("user="+user);
SqlSession session2 = MybatisUtils.getSession();
user = session2.selectOne(statement, 1);
session.commit();
System.out.println("user2="+user);
}

9.3.3.補(bǔ)充說(shuō)明

1. 映射語(yǔ)句文件中的所有select語(yǔ)句將會(huì)被緩存。

2. 映射語(yǔ)句文件中的所有insert，update和delete語(yǔ)句會(huì)刷新緩存。

3. 緩存會(huì)使用Least Recently Used（LRU，最近最少使用的）算法來(lái)收回。

4. 緩存會(huì)根據(jù)指定的時(shí)間間隔來(lái)刷新。

5. 緩存會(huì)存儲(chǔ)1024個(gè)對(duì)象

<cache
eviction="FIFO" //回收策略為先進(jìn)先出
flushInterval="60000" //自動(dòng)刷新時(shí)間60s
size="512" //最多緩存512個(gè)引用對(duì)象
readOnly="true"/> //只讀

十、Spring集成MyBatis

10.1.添加jar

【mybatis】

mybatis-3.2.0.jar
mybatis-spring-1.1.1.jar
log4j-1.2.17.jar

【spring】

spring-aop-3.2.0.RELEASE.jar
spring-beans-3.2.0.RELEASE.jar
spring-context-3.2.0.RELEASE.jar
spring-core-3.2.0.RELEASE.jar
spring-expression-3.2.0.RELEASE.jar
spring-jdbc-3.2.0.RELEASE.jar
spring-test-3.2.4.RELEASE.jar
spring-tx-3.2.0.RELEASE.jar
aopalliance-1.0.jar
cglib-nodep-2.2.3.jar
commons-logging-1.1.1.jar

【MYSQL驅(qū)動(dòng)包】

mysql-connector-java-5.0.4-bin.jar

10.2.數(shù)據(jù)庫(kù)表

CREATE TABLE s_user(
user_id INT AUTO_INCREMENT PRIMARY KEY,
user_name VARCHAR(30),
user_birthday DATE,
user_salary DOUBLE
)

10.3.實(shí)體類：User

public class User {
private int id;
private String name;
private Date birthday;
private double salary;
//set,get方法
}

10.4.DAO接口: UserMapper (XXXMapper)

public interface UserMapper {
void save(User user);
void update(User user);
void delete(int id);
User findById(int id);
List<User> findAll();
}

10.5.SQL映射文件: userMapper.xml(與接口忽略大小寫(xiě)同名)

<?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.atguigu.mybatis.test9.UserMapper">
<resultMap type="User" id="userResult">
<result column="user_id" property="id"/>
<result column="user_name" property="name"/>
<result column="user_birthday" property="birthday"/>
<result column="user_salary" property="salary"/>
</resultMap>
<!-- 取得插入數(shù)據(jù)后的id -->
<insert id="save" keyColumn="user_id" keyProperty="id" useGeneratedKeys="true">
insert into s_user(user_name,user_birthday,user_salary)
values(#{name},#{birthday},#{salary})
</insert>
<update id="update">
update s_user
set user_name = #{name},
user_birthday = #{birthday},
user_salary = #{salary}
where user_id = #{id}
</update>
<delete id="delete">
delete from s_user
where user_id = #{id}
</delete>
<select id="findById" resultMap="userResult">
select *
from s_user
where user_id = #{id}
</select>
<select id="findAll" resultMap="userResult">
select *
from s_user
</select>
</mapper>

10.6.spring的配置文件: beans.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:p="http://www.springframework.org/schema/p"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:tx="http://www.springframework.org/schema/tx"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.2.xsd
http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx-3.2.xsd">
<!-- 1. 數(shù)據(jù)源 : DriverManagerDataSource -->
<bean id="dataSource"
class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/mybatis"/>
<property name="username" value="root"/>
<property name="password" value="root"/>
</bean>
<!--
2. mybatis的SqlSession的工廠: SqlSessionFactoryBean
dataSource / typeAliasesPackage
-->
<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
<property name="dataSource" ref="dataSource"/>
<property name="typeAliasesPackage" value="com.atuigu.spring_mybatis2.domain"/>
</bean>
<!--
3. mybatis自動(dòng)掃描加載Sql映射文件 : MapperScannerConfigurer
sqlSessionFactory / basePackage
-->
<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
<property name="basePackage" value="com.atuigu.spring_mybatis2.mapper"/>
<property name="sqlSessionFactory" ref="sqlSessionFactory"/>
</bean>
<!-- 4. 事務(wù)管理 : DataSourceTransactionManager -->
<bean id="txManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
<property name="dataSource" ref="dataSource"/>
</bean>
<!-- 5. 使用聲明式事務(wù) -->
<tx:annotation-driven transaction-manager="txManager" />
</beans>

10.7.mybatis的配置文件: mybatis-config.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>
<!-- Spring整合myBatis后，這個(gè)配置文件基本可以不要了-->
<!-- 設(shè)置外部配置文件 -->
<!-- 設(shè)置類別名 -->
<!-- 設(shè)置數(shù)據(jù)庫(kù)連接環(huán)境 -->
<!-- 映射文件 -->
</configuration>

10.8.測(cè)試

@RunWith(SpringJUnit4ClassRunner.class) //使用Springtest測(cè)試框架
@ContextConfiguration("/beans.xml") //加載配置
public class SMTest {
@Autowired //注入
private UserMapper userMapper;
@Test
public void save() {
User user = new User();
user.setBirthday(new Date());
user.setName("marry");
user.setSalary(300);
userMapper.save(user);
System.out.println(user.getId());
}
@Test
public void update() {
User user = userMapper.findById(2);
user.setSalary(2000);
userMapper.update(user);
}
@Test
public void delete() {
userMapper.delete(3);
}
@Test
public void findById() {
User user = userMapper.findById(1);
System.out.println(user);
}
@Test
public void findAll() {
List<User> users = userMapper.findAll();
System.out.println(users);
}
}

以上所述是小編給大家介紹的MyBatis快速入門(mén)(簡(jiǎn)明淺析易懂)，希望對(duì)大家有所幫助，如果大家有任何疑問(wèn)請(qǐng)給我留言，小編會(huì)及時(shí)回復(fù)大家的。在此也非常感謝大家對(duì)腳本之家網(wǎng)站的支持！

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