Mybatis 快速入門(XML方式)第一天
阿新 • • 發佈：2020-05-16
導讀
架構原理圖
說明
mybatis配置檔案
- SqlMapConfig.xml，此檔案為mybatis的全域性配置檔案，配置了mybatis的執行環境等資訊
- XXXMapper.xml，此檔案作為mybatis的sql對映檔案，檔案中配置了操作資料庫的CRUD語句。需要在SqlMapConfig.xml中載入
SqlSessionFactory
- 通過mybatis環境等配置資訊構造SqlSessionFactory，既會話工廠
***跟底層原始碼檢視建立SqlSessionFactory流程***
注：底層如何獲取標籤值，請自行研究(劇透：for迴圈遍歷XML獲取標籤中的值，然後放入Map)！~
SqlSession
- 通過會員工廠建立SqlSession即會話，程式通過SqlSession會話介面對資料庫進行CRUD操作。
Executor執行器
mybatis底層自定義了Executor執行器介面來具體操作資料庫，Executor介面有兩個實現，一個是基本執行器(預設)，一個快取執行器，SqlSession底層是通過executor介面操作資料庫
Mapped Statement
他是mybatis一個底層封裝物件，包裝了mybatis配置資訊及XXXMapper.xml對映檔案等。XXXMapper.xml檔案中一個個select/insert/update/delete標籤對應一個Mapped Statement物件。
原始JDBC程式碼
原始JDBC和mybatis操作資料庫資料，與上面架構圖流程相對應。
public class JDBCTest {
public static void main(String[] args) {
Connection connection = null;
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
try {
// 載入資料庫驅動
Class.forName("com.mysql.jdbc.Driver");
// 通過驅動管理類獲取資料庫連結connection = DriverManager
connection = DriverManager.getConnection(
"jdbc:mysql://localhost:3306/mybatis?characterEncoding=utf-8",
"root",
"root"
);
// 定義sql語句 ?表示佔位符
String sql = "select * from user where username = ?";
// 獲取預處理 statement
preparedStatement = connection.prepareStatement(sql);
// 設定引數，第一個引數為 sql 語句中引數的序號（從 1 開始），第二個引數為設定的
preparedStatement.setString(1, "王五");
// 向資料庫發出 sql 執行查詢，查詢出結果集
resultSet = preparedStatement.executeQuery();
// 遍歷查詢結果集
while (resultSet.next()) {
System.out.println(
resultSet.getString("id")
+ " " +
resultSet.getString("username")
);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
// 釋放資源
if (resultSet != null) {
try {
resultSet.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (preparedStatement != null) {
try {
preparedStatement.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (connection != null) {
try {
connection.close();
} catch (SQLException e) {
// TODO Auto-generated catch block e.printStackTrace();
}
}
}
}
}Mybatis 入門基礎
表結構
表資料
Mybatis環境搭建
新增依賴
pom.xml
<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/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.cyb</groupId>
<artifactId>mybatis</artifactId>
<packaging>war</packaging>
<version>0.0.1-SNAPSHOT</version>
<name>mybatis Maven Webapp</name>
<url>http://maven.apache.org</url>
<dependencies>
<!-- mybatis依賴 -->
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.4.6</version>
</dependency>
<!-- mysql依賴 -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.20</version>
</dependency>
<!-- 單元測試 -->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
</dependency>
</dependencies>
<build>
<finalName>mybatis</finalName>
</build>
</project>
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>
<!-- 引入外部配置檔案 -->
<properties resource="db.properties"></properties>
<!-- 資料庫連結相關 -->
<environments default="development">
<environment id="development">
<transactionManager type="JDBC" />
<dataSource type="POOLED">
<property name="driver" value="${db.driver}" />
<property name="url" value="${db.url}" />
<property name="username" value="${db.username}" />
<property name="password" value="${db.password}" />
</dataSource>
</environment>
</environments>
<mappers>
<!-- 新增對映檔案 -->
<mapper resource="UserMapper.xml" />
</mappers>
</configuration>
db.properties
db.driver=com.mysql.jdbc.Driver db.url=jdbc:mysql://127.0.0.1:3306/cyb db.username=root db.password=root
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:為了分類管理對映檔案中的MappedStatement -->
<mapper namespace="test">
<select id="queryUserById" parameterType="int" resultType="com.cyb.mybatis.demo.User">
select * from user where id = #{id}
</select>
</mapper>
User.java
package com.cyb.mybatis.demo;
import java.util.Date;
public class User {
private int id;
private String username;
private Date birthday;
private int sex;
private String address;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
public int getSex() {
return sex;
}
public void setSex(int sex) {
this.sex = sex;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
@Override
public String toString() {
return "User [id=" + id + ", username=" + username + ", birthday=" + birthday + ", sex=" + sex + ", address="
+ address + "]";
}
}
MybatisDemo.java
package com.cyb.mybatis.demo;
import java.io.InputStream;
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.Before;
import org.junit.Test;
public class MybatisDemo {
private SqlSessionFactory sqlSessionFactory;
@Before
public void init() throws Exception {
//指定全域性配置檔案路徑
String resource = "SqlMapConfig.xml";
//載入資原始檔(包括全域性檔案和對映檔案)
InputStream inputStream = Resources.getResourceAsStream(resource);
//使用構建者模式建立SqlSessionFactory
sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
}
@Test
public void testSelect() {
//由SqlSessionFactory工廠去建立SqlSession(會話)
SqlSession sqlSession = sqlSessionFactory.openSession();
//呼叫SqlSession介面，去實現資料庫的CRUD
User user = sqlSession.selectOne("test.queryUserById", 1);
System.out.println(user);
//釋放資源
sqlSession.close();
}
}