mybatis進階
1.輸入對映和輸出對映
Mapper.xml對映檔案中定義了操作資料庫的sql,每個sql是一個statement,對映檔案是mybatis的核心
UserMapper.xml檔案中的配置:select標籤(parameterType,resultType,resultMap),if、sql、where、foreach標籤
1>parameterType:傳入引數型別
簡單型別:Integer,String....使用#{}佔位符,或者${}進行sql拼接。
pojo物件:User物件,Orders物件.....使用ognl表示式解析物件欄位的值,#{}或者${}括號中的值為pojo屬性名稱
QueryVo包裝物件(User為QueryVo的屬性):
<!-- 根據vo查
public List<User> findByVo(QueryVo vo); -->
<select id="findByVo" parameterType="QueryVo" resultType="User">
select * from user where username = #{user.username}
</select>
2>resultType:輸出引數型別
簡單型別:Integer,String...
pojo物件:User物件,Orders物件.....
3>resultMap:自動封裝輸出引數
<!--當pojo中的屬性名與資料庫列名不對應時,我們使用resultMap手動對映,只封裝我們想要(name不同)的屬性即可 --> <!-- id:設定主鍵 property:主鍵在pojo中的屬性名 column:主鍵在資料庫中的列名 --> <resultMap type="Orders" id="texOrders"> <result column="user_id" property="userId"/> </resultMap> <!-- 查詢訂單表order的所有資料 public List<Orders> findAll() --> <select id="findAll" resultMap="texOrders" > select * from orders </select>
2.動態SQL
if、sql、where、foreach標籤
1>sql:相同sql的抽取(如:select * from user)
<!-- sql片段抽取 -->
<sql id="texSql">
select * from user
</sql>
<select id="findByIds" resultType="User">
<include refid="texSql"/>
</select>
2>if:查詢前先進行判斷
<!-- 根據性別和名字查詢使用者
public List<User> findByUsernameANDSex(User user); -->
<select id="findByUsernameANDSex" parameterType="User" resultType="user">
<if test="username != null and username != ''">
AND username = #{username}
</if>
<if test="sex != null and sex != ''">
AND sex = #{sex}
</if>
</select>
3>where:去掉前and(不能去掉後and)
<!-- 根據性別和名字查詢使用者
public List<User> findByUsernameANDSex(User user); -->
<select id="findByUsernameANDSex" parameterType="User" resultType="user">
<include refid="texSql"/>
<where>
<if test="username != null and username != ''">
AND username = #{username}
</if>
<if test="sex != null and sex != ''">
AND sex = #{sex}
</if>
</where>
</select>
4>foreach:迴圈遍歷(
當傳入的是QueryVo時,foreach中的collection值直接寫QueryVo中的屬性名即可,
當傳入的是Integer[]型別時,mybatis會將傳入名改變為array,所以collection值填寫array
當傳入的是List<Integer>型別時,mybatis會將傳入名改變為list,所以collection值填寫list
)
<!-- //根據ids查詢使用者
List<User> findByIds(QueryVo ids);
List<User> findByIds2(Integer[] ids);//array
List<User> findByIds3(List<Integer> ids);//list -->
<select id="findByIds" parameterType="QueryVo" resultType="User">
<include refid="texSql"/>
<where>
id in
<foreach collection="idsList" item="ids" open="(" close=")" separator=",">
#{ids}
</foreach>
</where>
</select>
<select id="findByIds2" parameterType="Integer" resultType="User">
<include refid="texSql"/>
<where>
id in
<foreach collection="array" item="ids" open="(" close=")" separator=",">
#{ids}
</foreach>
</where>
</select>
<select id="findByIds3" parameterType="Integer" resultType="User">
<include refid="texSql"/>
<where>
id in
<foreach collection="list" item="ids" open="(" close=")" separator=",">
#{ids}
</foreach>
</where>
</select>
3.關聯查詢(劃重點)
一對一:一個訂單隻能由一個使用者建立,一對多:一個使用者可以建立多個訂單
一對一查詢:使用resultMap中的association
1>在orders表中宣告user
//表達一對一
private User user;get/set
2>OrdersMapper.xml對映檔案中表達
<!-- //表達一對一關係
public List<Orders> findByOneToOne(); -->
<resultMap type="Orders" id="resOrder">
<id column="id" property="id"/>
<result column="number" property="number"/>
<!-- 一對一關係內部表達 -->
<association property="user" javaType="User">
<id column="user_id" property="id"/>
<result column="username" property="username"/>
</association>
</resultMap>
<select id="findByOneToOne" resultMap="resOrder">
SELECT
o.id,
o.number,
o.user_id,
u.username
FROM
orders o LEFT JOIN USER u
ON o.user_id = u.id
</select>
一對多查詢:使用resultMap中的association
1>在User中宣告List<Orders>
//表達一對多關係
private List<Orders> ordList;get/set
2>UserMapper.xml對映檔案中表達
<!-- //表達多對多關係
public User findByMoreToMore(); -->
<resultMap type="User" id="resUser">
<id column="user_id" property="id"/>
<result column="username" property="username"/>
<!-- 表達多對多關係 -->
<collection property="ordList" ofType="Orders">
<id column="id" property="id"/>
<result column="number" property="number"/>
</collection>
</resultMap>
<select id="findByMoreToMore" resultMap="resUser">
SELECT
o.id,
o.number,
o.user_id,
u.username
FROM USER u LEFT JOIN orders o
ON o.user_id = u.id
</select>
4.mybatis與spring的整合(劃重點)
1>整合思路
SqlSessionFactory物件應該放到spring容器中作為單例存在。
Mapper代理形式中,應該從spring容器中直接獲得mapper的代理物件。
資料庫的連線以及資料庫連線池事務管理都交給spring容器來完成
2>所需jar包
spring的jar包、Mybatis的jar包、Spring+mybatis的整合包、mysql資料庫驅動包、連線池包
3>applciationContext.xml配置檔案
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:context="http://www.springframework.org/schema/context" xmlns:p="http://www.springframework.org/schema/p"
xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd
http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsd
http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-4.0.xsd">
<!-- 載入配置檔案 -->
<context:property-placeholder location="classpath:db.properties" />
<!-- 資料庫連線池 -->
<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource"
destroy-method="close">
<property name="driverClassName" value="${jdbc.driver}" />
<property name="url" value="${jdbc.url}" />
<property name="username" value="${jdbc.username}" />
<property name="password" value="${jdbc.password}" />
<property name="maxActive" value="10" />
<property name="maxIdle" value="5" />
</bean>
<!-- 配置SqlSessionFactory -->
<bean id="sqlSessionFactoryBean" class="org.mybatis.spring.SqlSessionFactoryBean">
<!-- 配置mybatis核心配置檔案 -->
<property name="configLocation" value="sqlMapConfig.xml" />
<!-- 配置資料來源 -->
<property name="dataSource" ref="dataSource" />
</bean>
<!-- Mapper動態代理開發
<bean id="userMapper" class="org.mybatis.spring.mapper.MapperFactoryBean">
<property name="sqlSessionFactory" ref="sqlSessionFactoryBean"/>
<property name="mapperInterface" value="com.imwj.mapper.UserMapper"/>
</bean> -->
<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
<!-- 路徑基本包 -->
<property name="basePackage" value="com.imwj.mapper"/>
</bean>
</beans>
db.properties:
jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/mybatis?characterEncoding=utf-8
jdbc.username=root
jdbc.password=123456
4>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>
<typeAliases>
<!-- 2. 指定掃描包,會把包內所有的類都設定別名,別名的名稱就是類名,大小寫不敏感 -->
<package name="com.imwj.pojo" />
</typeAliases>
<mappers>
<!-- 掃描整個包路徑 -->
<package name="com.imwj.mapper"/>
</mappers>
</configuration>
5>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">
<!-- namespace:名稱空間,用於隔離sql,還有一個很重要的作用,後面會講 -->
<mapper namespace="com.imwj.mapper.UserMapper">
<!-- 根據id查詢 -->
<select id="findById" parameterType="Integer" resultType="User">
select * from user where id = #{id}
</select>
</mapper>
6>UserMapper.java
public interface UserMapper {
//根據id查詢
public User findById(Integer id);
7>測試
@Test
public void fun2(){
ClassPathXmlApplicationContext apx = new ClassPathXmlApplicationContext("classpath:applicationContext.xml");
UserMapper mapper = (UserMapper) apx.getBean("userMapper");
User user = mapper.findById(1);
System.out.println(user);
}
6.逆向工程
簡單點說,就是通過資料庫中的單表,自動生成java程式碼。
Mybatis官方提供了逆向工程,可以針對單表自動生成mybatis程式碼(mapper.java\mapper.xml\po類)
2>生成檔案
3>使用
@Test
public void fun1(){
ClassPathXmlApplicationContext ac = new ClassPathXmlApplicationContext("classpath:applicationContext.xml");
UserMapper userMapper = ac.getBean(UserMapper.class);
UserExample userExample = new UserExample();
userExample.createCriteria().andUsernameLike("%張%");
List<User> users = userMapper.selectByExample(userExample);
for (User user : users) {
System.out.println(user);
}
}