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mybatis學習筆記(3)-入門程序一
標簽： mybatis
[TOC]
工程結構
在IDEA中新建了一個普通的java項目，新建文件夾lib,加入jar包,工程結構如圖。
# Global logging configuration
log4j.rootLogger=DEBUG, stdout
# Console output...
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configurationPUBLIC "-//mybatis.org//DTD Config 3.0//EN""http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration><!-- 和spring整合后 environments配置將廢除--><environments default="development"><environment id="development"><!-- 使用jdbc事務管理，事務控制由mybatis--><transactionManager type="JDBC" /><!-- 數據庫連接池,由mybatis管理--><dataSource type="POOLED"><property name="driver" value="com.mysql.jdbc.Driver" /><property name="url" value="jdbc:mysql://120.25.162.238:3306/mybatis001?characterEncoding=utf-8" /><property name="username" value="root" /><property name="password" value="123" /></dataSource></environment></environments></configuration>
映射文件
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!-- namespace 命名空間，作用就是對sql進行分類化管理,理解為sql隔離注意：使用mapper代理方法開發，namespace有特殊重要的作用-->
<mapper namespace="test"><!-- 在映射文件中配置很多sql語句 --><!--需求:通過id查詢用戶表的記錄 --><!-- 通過select執行數據庫查詢id:標識映射文件中的sql，稱為statement的id將sql語句封裝到mappedStatement對象中，所以將id稱為statement的idparameterType:指定輸入參數的類型#{}標示一個占位符,#{value}其中value表示接收輸入參數的名稱，如果輸入參數是簡單類型，那么#{}中的值可以任意。resultType：指定sql輸出結果的映射的java對象類型，select指定resultType表示將單條記錄映射成java對象--><select id="findUserById" parameterType="int" resultType="com.iot.mybatis.po.User">SELECT * FROM user WHERE id=#{value}</select><!-- 根據用戶名稱模糊查詢用戶信息，可能返回多條resultType：指定就是單條記錄所映射的java對象類型${}:表示拼接sql串，將接收到參數的內容不加任何修飾拼接在sql中。使用${}拼接sql，引起 sql注入${value}：接收輸入參數的內容，如果傳入類型是簡單類型，${}中只能使用value--><select id="findUserByName" parameterType="java.lang.String" resultType="com.iot.mybatis.po.User">SELECT * FROM user WHERE username LIKE '%${value}%'</select></mapper>
在sqlMapConfig.xml中加載User.xml
<!-- 加載映射文件-->
<mappers><mapper resource="sqlmap/User.xml"/>
</mappers>
程序代碼
package com.iot.mybatis.po;import java.util.Date;/*** Created by Administrator on 2016/2/21.*/
public class User {//屬性名要和數據庫表的字段對應private int id;private String username;// 用戶姓名private String sex;// 性別private Date birthday;// 生日private String address;// 地址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 String getSex() {return sex;}public void setSex(String sex) {this.sex = sex;}public Date getBirthday() {return birthday;}public void setBirthday(Date birthday) {this.birthday = birthday;}public String getAddress() {return address;}public void setAddress(String address) {this.address = address;}@Overridepublic String toString() {return "User [id=" + id + ", username=" + username + ", sex=" + sex+ ", birthday=" + birthday + ", address=" + address + "]";}
}
package com.iot.mybatis.first;import com.iot.mybatis.po.User;
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.Test;import java.io.IOException;
import java.io.InputStream;
import java.util.List;/*** Created by Administrator on 2016/2/23.*/
public class MybatisFirst {//根據id查詢用戶信息，得到一條記錄結果@Testpublic void findUserByIdTest() throws IOException{// mybatis配置文件String resource = "SqlMapConfig.xml";// 得到配置文件流InputStream inputStream = Resources.getResourceAsStream(resource);//創建會話工廠，傳入mybatis配置文件的信息SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);// 通過工廠得到SqlSessionSqlSession sqlSession = sqlSessionFactory.openSession();// 通過SqlSession操作數據庫// 第一個參數：映射文件中statement的id，等于=namespace+"."+statement的id// 第二個參數：指定和映射文件中所匹配的parameterType類型的參數// sqlSession.selectOne結果 是與映射文件中所匹配的resultType類型的對象// selectOne查詢出一條記錄User user = sqlSession.selectOne("test.findUserById", 1);System.out.println(user);// 釋放資源sqlSession.close();}// 根據用戶名稱模糊查詢用戶列表@Testpublic void findUserByNameTest() throws IOException {// mybatis配置文件String resource = "SqlMapConfig.xml";// 得到配置文件流InputStream inputStream = Resources.getResourceAsStream(resource);// 創建會話工廠，傳入mybatis的配置文件信息SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);// 通過工廠得到SqlSessionSqlSession sqlSession = sqlSessionFactory.openSession();// list中的user和映射文件中resultType所指定的類型一致List<User> list = sqlSession.selectList("test.findUserByName", "小明");System.out.println(list);sqlSession.close();}}
輸出：
DEBUG [main] - Logging initialized using 'class org.apache.ibatis.logging.slf4j.Slf4jImpl' adapter.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - Opening JDBC Connection
DEBUG [main] - Created connection 1857815974.
DEBUG [main] - Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@6ebc05a6]
DEBUG [main] - ==> Preparing: SELECT * FROM user WHERE id=?
DEBUG [main] - ==> Parameters: 1(Integer)
DEBUG [main] - <== Total: 1
User [id=1, username=王五, sex=2, birthday=null, address=null]
DEBUG [main] - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@6ebc05a6]
DEBUG [main] - Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@6ebc05a6]
DEBUG [main] - Returned connection 1857815974 to pool.
DEBUG [main] - Logging initialized using 'class org.apache.ibatis.logging.slf4j.Slf4jImpl' adapter.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - Opening JDBC Connection
DEBUG [main] - Created connection 1596467899.
DEBUG [main] - Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@5f282abb]
DEBUG [main] - ==> Preparing: SELECT * FROM user WHERE username LIKE '%小明%'
DEBUG [main] - ==> Parameters:
DEBUG [main] - <== Total: 3
[User [id=16, username=張小明, sex=1, birthday=null, address=河南鄭州], User [id=22, username=陳小明, sex=1, birthday=null, address=河南鄭州], User [id=25, username=陳小明, sex=1, birthday=null, address=河南鄭州]]
DEBUG [main] - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@5f282abb]
DEBUG [main] - Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@5f282abb]
DEBUG [main] - Returned connection 1596467899 to pool.
總結
在映射文件中通過parameterType指定輸入參數的類型
在映射文件中通過resultType指定輸出結果的類型
org.apache.ibatis.exceptions.TooManyResultsException: Expected one result (or null) to be returned by selectOne(), but found: 3
作者@brianway更多文章：個人網站 | CSDN | oschina
轉載于:https://my.oschina.net/brianway/blog/625244
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