學習一個新的組件，一要看需要哪些JAR包，二要看需要哪些配置，三要看API如何使用。
0、準備Emp數據表
MySQL語法
create table emp( id int(5) primary key, name varchar(10), sal double(8,2) );
Oracle語法
create table emp( id number(5) primary key, name varchar2(10), sal number(8,2) );
1、新建web工程，添加jar
需要的jar包包括三部分：mybatis的jar包、mybatis依賴的jar包、數據庫驅動包
我使用的mybatis版本是mybatis-3.2.7
| mybatis | mybatis-3.2.7.jar |
| mybatis的依賴包 | 位於lib目錄下 asm-3.3.1.jar cglib-2.2.2.jar commons-logging-1.1.1.jar log4j-1.2.17.jar |
| 數據庫驅動 | MySQL mysql-connector-java-5.1.38-bin.jar 或 Oracle ojdbc5.jar |
log4j的配置文件，放到src目錄下
log4j.properties
log4j.rootLogger=debug,stdout,logfile
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.SimpleLayout
log4j.appender.logfile=org.apache.log4j.FileAppender
log4j.appender.logfile.layout=org.apache.log4j.PatternLayout
log4j.appender.logfile.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} %F %p %m%n
log4j.logger.com.ibatis=DEBUG
log4j.logger.com.ibatis.common.jdbc.SimpleDataSource=DEBUG
log4j.logger.com.ibatis.common.jdbc.ScriptRunner=DEBUG
log4j.logger.com.ibatis.sqlmap.engine.impl.SqlMapClientDelegate=DEBUG
log4j.logger.java.sql.Connection=DEBUG
log4j.logger.java.sql.Statement=DEBUG
log4j.logger.java.sql.PreparedStatement=DEBUG2、創建Emp.java
Emp.java
package com.rk.entity;
public class Emp {
private Integer id;
private String name;
private Double sal;
public Emp(){}
public Emp(Integer id, String name, Double sal) {
this.id = id;
this.name = name;
this.sal = sal;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Double getSal() {
return sal;
}
public void setSal(Double sal) {
this.sal = sal;
}
}3、在entity包下添加EmpMapper.xml文件
EmpMapper.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屬性是名稱空間，必須唯一 -->
<mapper namespace="mynamespace">
<!--
insert標籤：要書寫insert這麼一個sql語句
id屬性：爲insert這麼一個sql語句取一個任意唯一的名字
parameterType:要執行的dao中的方法的參數，如果是類的話，必須使用全路徑類
-->
<insert id="add1">
insert into emp(id,name,sal) values(1,'Tomcat',800)
</insert>
<!-- 這裏用的是類的全路徑：com.rk.entity.Emp -->
<insert id="add2" parameterType="com.rk.entity.Emp">
insert into emp(id,name,sal) values(#{id},#{name},#{sal});
</insert>
</mapper>4、在src目錄下創建mybatis.xml文件
mybatis.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://127.0.0.1:3306/testdb"/> <property name="username" value="root"/> <property name="password" value="root"/> </dataSource> </environment> </environments> <mappers> <mapper resource="com/rk/entity/EmpMapper.xml"/> </mappers> </configuration>
5、在utils包下添加MyBatisUtils.java，並進行測試是否能夠連接數據庫
MyBatisUtils.java
package com.rk.utils;
import java.io.IOException;
import java.io.Reader;
import java.sql.Connection;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
public class MyBatisUtils {
private static ThreadLocal<SqlSession> threadLocal = new ThreadLocal<SqlSession>();
private static SqlSessionFactory sqlSessionFactory;
static{
try {
Reader reader = Resources.getResourceAsReader("mybatis.xml");
sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
} catch (IOException e) {
e.printStackTrace();
throw new RuntimeException(e);
}
}
private MyBatisUtils() {}
public static SqlSession getSqlSession(){
SqlSession sqlSession = threadLocal.get();
if(sqlSession == null){
sqlSession = sqlSessionFactory.openSession();
threadLocal.set(sqlSession);
}
return sqlSession;
}
public static void closeSqlSession(){
SqlSession sqlSession = threadLocal.get();
if(sqlSession != null){
sqlSession.close();
threadLocal.remove();
}
}
public static void main(String[] args) {
Connection conn = MyBatisUtils.getSqlSession().getConnection();
System.out.println(conn!=null ? "連接成功" : "連接失敗");
}
}MyBatisUtils工具類的作用
1）在靜態初始化塊中加載mybatis配置文件和EmpMapper.xml文件
2）使用ThreadLocal對象讓當前線程與SqlSession對象綁定在一起
3）獲取當前線程中的SqlSession對象，如果沒有的話，從SqlSessionFactory對象中獲取SqlSession對象
4）關閉SqlSession，首先獲取當前線程中的SqlSession對象，再將其關閉，釋放其佔用的資源
6、在dao包下添加EmpDao.java，並進行測試
EmpDao.java
package com.rk.dao;
import org.apache.ibatis.session.SqlSession;
import com.rk.entity.Emp;
import com.rk.utils.MyBatisUtils;
public class EmpDao {
/**
* 添加員工（無參數）
*/
public void add1() throws Exception {
SqlSession sqlSession = null;
try{
sqlSession = MyBatisUtils.getSqlSession();
//事務開始（默認）
//讀取EmpMapper.xml映射文件中的SQL語句
int i = sqlSession.insert("mynamespace.add1");
System.out.println("本次操作影響"+i+"行數據");
//事務提交
sqlSession.commit();
}
catch(Exception e){
e.printStackTrace();
if(sqlSession != null){
//事務回滾
sqlSession.rollback();
}
}
finally{
MyBatisUtils.closeSqlSession();
}
}
/**
* 添加員工（帶參數）
*/
public void add2(Emp emp) throws Exception{
SqlSession sqlSession = null;
try{
sqlSession = MyBatisUtils.getSqlSession();
//事務開始（默認）
//讀取EmpMapper.xml映射文件中的SQL語句
int i = sqlSession.insert("mynamespace.add2",emp);
System.out.println("本次操作影響"+i+"行數據");
//事務提交
sqlSession.commit();
}
catch(Exception e){
e.printStackTrace();
if(sqlSession != null){
//事務回滾
sqlSession.rollback();
}
}
finally{
MyBatisUtils.closeSqlSession();
}
}
public static void main(String[] args) throws Exception {
EmpDao dao = new EmpDao();
dao.add1();
dao.add2(new Emp(2,"小明",500D));
}
}輸出：
DEBUG - Logging initialized using 'class org.apache.ibatis.logging.commons.JakartaCommonsLoggingImpl' adapter. DEBUG - PooledDataSource forcefully closed/removed all connections. DEBUG - PooledDataSource forcefully closed/removed all connections. DEBUG - PooledDataSource forcefully closed/removed all connections. DEBUG - PooledDataSource forcefully closed/removed all connections. DEBUG - Opening JDBC Connection DEBUG - Created connection 236749989. DEBUG - Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@e1c84a5] DEBUG - ==> Preparing: insert into emp(id,name,sal) values(1,'Tomcat',800) DEBUG - ==> Parameters: DEBUG - <== Updates: 1 本次操作影響1行數據 DEBUG - Committing JDBC Connection [com.mysql.jdbc.JDBC4Connection@e1c84a5] DEBUG - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@e1c84a5] DEBUG - Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@e1c84a5] DEBUG - Returned connection 236749989 to pool. DEBUG - Opening JDBC Connection DEBUG - Checked out connection 236749989 from pool. DEBUG - Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@e1c84a5] DEBUG - ==> Preparing: insert into emp(id,name,sal) values(?,?,?); DEBUG - ==> Parameters: 2(Integer), 小明(String), 500.0(Double) DEBUG - <== Updates: 1 本次操作影響1行數據 DEBUG - Committing JDBC Connection [com.mysql.jdbc.JDBC4Connection@e1c84a5] DEBUG - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@e1c84a5] DEBUG - Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@e1c84a5] DEBUG - Returned connection 236749989 to pool.
7、MyBatis工作流程
1）通過Reader對象讀取src目錄下的mybatis.xml配置文件(該文件的位置和名字可以任意)
2）通過SqlSessionFactoryBuilder對象創建SqlSessionFactory對象
3）從當前線程中獲取SqlSession對象
4）事務開始，在mybatis中默認
5）通過SqlSession對象讀取EmpMapper.xml映射文件中的操作編號，從而讀取sql語句
6）事務提交（必寫）
7）關閉SqlSession對象，並且分開當前線程與SqlSession對象，讓GC儘早回收