9.Mybatis在網站專案裡的使用
阿新 • • 發佈：2020-12-09
技術標籤：MyBatis學習筆記mybatis
本次測試的目的是實現tomcat啟動時同時初始化mybatis
步驟如下：
1.匯入資料庫，新增pojo。（資料庫使用到的是之前的student表，Student的POJO類也是之前的）
/*
SQLyog Ultimate v11.24 (32 bit)
MySQL - 5.6.39 : Database - af_example
*********************************************************************
*/
/*!40101 SET NAMES utf8 */;
/*!40101 SET SQL_MODE=''*/;
/*!40014 SET @ 
package my.db; public class Student { public Integer id; public String name; public Boolean sex; public String cellphone; 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 Boolean getSex() { return sex; } public void setSex(Boolean sex) { this.sex = sex; } public String getCellphone() { return cellphone; } public void setCellphone(String cellphone) { this.cellphone = cellphone; } }
2.在網站專案裡匯入本次測試需要的jar包，相比之前添加了一個json支援
3.複製以下檔案到src根目錄
- 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>
<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/af_example?useUnicode=true&characterEncoding=UTF-8"/>
<property name="username" value="root"/>
<property name="password" value="a1b2c3"/>
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="mybatis-mapper.xml"/>
</mappers>
</configuration>- mybatis-mapper.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="af.test">
<select id="getStudent" resultType="my.db.Student">
select * from student where id=#{id}
</select>
</mapper>- log4j.properties
# C,R is name of the following appenders
log4j.logger.af.test=DEBUG,C,R
log4j.appender.C=org.apache.log4j.ConsoleAppender
# Set the appender threshold to INFO
log4j.appender.C.Threshold=DEBUG
log4j.appender.C.layout=org.apache.log4j.PatternLayout
log4j.appender.C.layout.ConversionPattern=%-d{yyyy-MM-dd HH:mm:ss} %-5p [XYZ] %c %x - %m%n
# logging to file, rolling
# - change the log file's name and path, located in tomcat path
log4j.appender.R=org.apache.log4j.RollingFileAppender
log4j.appender.R.Threshold=DEBUG
log4j.appender.R.File=c:/mylogs/mybatis-example.log
log4j.appender.R.MaxFileSize=4000KB
# Keep one backup file
log4j.appender.R.MaxBackupIndex=1
log4j.appender.R.layout=org.apache.log4j.PatternLayout
log4j.appender.R.layout.ConversionPattern=%-d{yyyy-MM-dd HH:mm:ss} %-5p %c %x - %m%n
4.建立一個MyBatis類
- static靜態程式碼塊並不是程式啟動時就執行，而在首次呼叫這個類的時候執行，只執行一次。
- 全域性例項：在程式執行期間一直存在的物件，使用 static 修飾的引用為全域性例項，SqlSessionFactory應該建立為全域性例項。
package my.db;
import java.io.IOException;
import java.io.InputStream;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
public class MyBatis
{
// 全域性例項
public static SqlSessionFactory sqlSessionFactory;
// 靜態程式碼塊: 初始化 SqlSessionFactory 例項
static
{
System.out.println("*******************mybatis初始化*******************");
try
{
String resource="mybatis-config.xml";
InputStream inputStream=Resources.getResourceAsStream(resource);
sqlSessionFactory=new SqlSessionFactoryBuilder().build(inputStream);
} catch (IOException e)
{
e.printStackTrace();
}
}
//隨便新增一個方法
public static void mybatisInit()
{
}
}
這個類也可以這樣寫，看起來更加通俗易懂
package my.db;
import java.io.IOException;
import java.io.InputStream;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
public class MyBatis
{
public static SqlSessionFactory sqlSessionFactory;
public static void mybatisInit()
{
System.out.println("*******************mybatis初始化*******************");
try
{
String resource="mybatis-config.xml";
InputStream inputStream=Resources.getResourceAsStream(resource);
sqlSessionFactory=new SqlSessionFactoryBuilder().build(inputStream);
} catch (IOException e)
{
e.printStackTrace();
}
}
}
5.建立一個Filter，用於mybatis在tomcat啟動時進行初始化，其中，不要忘了新增一個@WebFilter() 註解
- 按照Filter的基本原理，在Tomcat載入之時Filter會被初始化，Filter.init()會被執行。在Filter.init() 裡初始化全域性例項SqlSessionFactory。
package my.db;
import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;
@WebFilter()
public class Boot implements Filter
{
public void init(FilterConfig fConfig) throws ServletException
{
MyBatis.mybatisInit();
}
public void destroy()
{
}
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
throws IOException, ServletException
{
chain.doFilter(request, response);
}
}
6.建立一個Servlet用於測試
package my;
import java.io.IOException;
import java.io.Writer;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.ibatis.session.SqlSession;
import org.json.JSONObject;
import my.db.MyBatis;
import my.db.Student;
@WebServlet("/getStudent")
public class GetStudent extends HttpServlet
{
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
// TODO Auto-generated method stub
String id=request.getParameter("id");
JSONObject result = new JSONObject();
//MyBatis.factory 是一個全域性的工廠例項
try(SqlSession sqlSession=MyBatis.sqlSessionFactory.openSession())
{
Student row=sqlSession.selectOne("af.test.getStudent", id);
if(row != null)
{
result = new JSONObject(row);
}
else
{
response.sendError(404);
return;
}
}
// 應答
response.setCharacterEncoding("UTF-8");
response.setContentType("text/plain");
Writer writer=response.getWriter();
writer.write(result.toString(2));
writer.close();
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
// TODO Auto-generated method stub
doGet(request, response);
}
}
7.將網站專案部署到tomcat伺服器，這裡我就不具體說了，tomcat的server.xml裡新增一行
8.啟動伺服器，在瀏覽器裡輸入http://127.0.0.1:8080/demo/getStudent?id=20190001 可以看到已經得到結果
