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MyBatis基础入门《二》Select查询

　　使用MySQL数据库，创建表：

 1 SET NAMES utf8mb4;
 2 SET FOREIGN_KEY_CHECKS = 0;
 3 
 4 -- ----------------------------
 5 -- Table structure for tbl_client_copy1
 6 -- ----------------------------
 7 DROP TABLE IF EXISTS `tbl_client_copy1`;
 8 CREATE TABLE `tbl_client_copy1`  (
 9   `id` int(5) NOT NULL AUTO_INCREMENT,
10   `client_name` varchar(255) CHARACTER SET utf8 COLLATE utf8_unicode_ci NULL DEFAULT NULL,
11   `client_address` varchar(255) CHARACTER SET utf8 COLLATE utf8_unicode_ci NULL DEFAULT NULL,
12   `client_birthday` datetime NULL DEFAULT NULL,
13   PRIMARY KEY (`id`) USING BTREE
14 ) ENGINE = InnoDB AUTO_INCREMENT = 1 CHARACTER SET = utf8 COLLATE = utf8_unicode_ci ROW_FORMAT = Compact;
15 
16 SET FOREIGN_KEY_CHECKS = 1;

项目工程：

ClientMapper.xml

 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 <!DOCTYPE mapper
 3   PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
 4   "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
 5 
 6 <mapper namespace="com.charles.dao.ClientMapper">
 7         
 8     <!-- 查询数据库 -->
 9     <select id="getCount" resultType="int">
10         SELECT COUNT(*) FROM tbl_client
11     </select>    
12 
13 </mapper>

TblClient.java

 1 package com.charles.entity;
 2 
 3 import java.io.Serializable;
 4 
 5 public class TblClient implements Serializable {
 6 
 7     private static final long serialVersionUID = -5993993584624176849L;
 8 
 9     private Integer cid;
10     private String cname;
11     private String caddress;
12     private String cbirthday;
13 
14     public TblClient() {
15     }
16 
17     public Integer getCid() {
18         return cid;
19     }
20 
21     public void setCid(Integer cid) {
22         this.cid = cid;
23     }
24 
25     public String getCname() {
26         return cname;
27     }
28 
29     public void setCname(String cname) {
30         this.cname = cname;
31     }
32 
33     public String getCaddress() {
34         return caddress;
35     }
36 
37     public void setCaddress(String caddress) {
38         this.caddress = caddress;
39     }
40 
41     public String getCbirthday() {
42         return cbirthday;
43     }
44 
45     public void setCbirthday(String cbirthday) {
46         this.cbirthday = cbirthday;
47     }
48 
49 }

mybatis-config.xml

 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 <!DOCTYPE configuration
 3   PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
 4   "http://mybatis.org/dtd/mybatis-3-config.dtd">
 5 
 6 <configuration>
 7 
 8     <!-- 引入database.properties文件 -->
 9     <properties resource="properties/database.properties"></properties>
10 
11     <!-- 配置mybatis的log实现log4j -->
12     <settings>
13         <setting name="logImpl" value="STDOUT_LOGGING" />
14     </settings>
15 
16     <!-- 配置Mybatis的环境 -->
17     <environments default="development">
18         <environment id="development">
19             <!-- 配置事物管理 -->
20             <transactionManager type="JDBC" />
21             <dataSource type="POOLED">
22                 <property name="driver" value="${jdbc.driver}" />
23                 <property name="url" value="${jdbc.url}" />
24                 <property name="username" value="${jdbc.username}" />
25                 <property name="password" value="${jdbc.password}" />
26             </dataSource>
27         </environment>
28     </environments>
29 
30     <!-- 将Mapper文件加入到mybatis的配置文件中 -->
31     <mappers>
32         <mapper resource="com/charles/dao/ClientMapper.xml" />
33     </mappers>
34 
35 
36 </configuration>

database.properties

　　这个是链接数据库的配置，未做改动，不在显示：见《Mybatis基础入门《一》环境搭建》

log4j.properties

# Global logging configuration
log4j.rootLogger=ERROR, stdout
# MyBatis logging configuration...
log4j.logger.com.charles=TRACE
# 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

JunitMybatisConfig.java

 1 package com.charles.junit;
 2 
 3 import static org.junit.Assert.fail;
 4 
 5 import java.io.IOException;
 6 import java.io.InputStream;
 7 
 8 import org.apache.ibatis.io.Resources;
 9 import org.apache.ibatis.session.SqlSession;
10 import org.apache.ibatis.session.SqlSessionFactory;
11 import org.apache.ibatis.session.SqlSessionFactoryBuilder;
12 import org.apache.log4j.Logger;
13 import org.apache.log4j.PropertyConfigurator;
14 import org.junit.Test;
15 
16 public class JunitMybatisConfig {
17 
18     @Test
19     public void test() {
20         fail("Not yet implemented");
21     }
22 
23     @Test
24     public void testLog4j() {
25         PropertyConfigurator.configure("D:/DISK WORKSPACE/STS MAVEN/mybatis-base/src/main/resources/lo4j.properties");
26         Logger logger = Logger.getLogger(JunitMybatisConfig.class);
27         logger.debug(" debug ");
28         logger.error(" error ");
29     }
30 
31     @Test
32     public void testMybaits() {
33 
34         try {
35             /** 1.获取mybatis-config.xml文件 **/
36             String resource = "mybatis/mybatis-config.xml";
37             InputStream is = Resources.getResourceAsStream(resource);
38 
39             /** 2.创建SQLSessionFactory对象 **/
40             SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
41 
42             /** 3.创建SQLSession **/
43             SqlSession session = sqlSessionFactory.openSession();
44 
45             /** 4.输出SQLSession对象 **/
46             System.out.println(session);
47         } catch (IOException e) {
48             e.printStackTrace();
49         }
50     }
51 }

　　注意：

　　　　sqlSessionFactory.openSession(boolean autoCommit); 这里的openSession的方法中有一个boolean类型的参数。

　　　　　　true：关闭事物控制（默认）

　　　　　　false：开启事物控制

JunitMybatisSelect.java

 1 package com.charles.junit;
 2 
 3 import java.io.IOException;
 4 import java.io.InputStream;
 5 
 6 import org.apache.ibatis.io.Resources;
 7 import org.apache.ibatis.session.SqlSession;
 8 import org.apache.ibatis.session.SqlSessionFactory;
 9 import org.apache.ibatis.session.SqlSessionFactoryBuilder;
10 import org.junit.Test;
11 
12 public class JunitMybatisSelect {
13 
14     @Test
15     public void junitSelect() {
16         SqlSession session = null;
17         try {
18             /** 1.获取mybatis-config.xml文件 **/
19             String resource = "mybatis/mybatis-config.xml";
20             InputStream is = Resources.getResourceAsStream(resource);
21 
22             /** 2.创建SQLSessionFactory对象 **/
23             SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
24 
25             /** 3.创建SQLSession **/
26             session = sqlSessionFactory.openSession();
27 
28             /** 4.输出SQLSession对象 **/
29             System.out.println(session);
30             String resoruce = "com.charles.dao.ClientMapper.getCount";
31             int count = session.selectOne(resoruce);
32             System.out.println(count);
33             
34         } catch (IOException e) {
35             e.printStackTrace();
36         } finally {
37             if(null != session) {
38                 session.close();
39             }
40         }
41     }
42 }

　　注意：

　　　　String resource = "com.charles.dao.ClientMapper.getCount", 这个不是随便写的，这是由：ClientMapper.xml 文件中的namespace + select标签ID的值组成。

　　　　SQLSession的使用方式有两种:

　　　　　　1. 通过SQLSession的实例直接运行映射的SQL语句。

　　　　　　2. 基于Mapper接口方式操作数据。

　　　　由于是初步搭建学习MyBatis，这里我使用的是第一种。一步一步的深入，后面会改成第二种方式。

pom.xml

 1 <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 2     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
 3     <modelVersion>4.0.0</modelVersion>
 4     <groupId>com.charles.mybatis</groupId>
 5     <artifactId>mybatis-base</artifactId>
 6     <version>0.0.1-SNAPSHOT</version>
 7 
 8     <dependencies>
 9         <dependency>
10             <groupId>junit</groupId>
11             <artifactId>junit</artifactId>
12             <version>4.11</version>
13         </dependency>
14         <dependency>
15             <groupId>log4j</groupId>
16             <artifactId>log4j</artifactId>
17             <version>1.2.17</version>
18         </dependency>
19 <!--         <dependency> -->
20 <!--             <groupId>org.slf4j</groupId> -->
21 <!--             <artifactId>slf4j-api</artifactId> -->
22 <!--             <version>1.7.7</version> -->
23 <!--         </dependency> -->
24 <!--         <dependency> -->
25 <!--             <groupId>org.slf4j</groupId> -->
26 <!--             <artifactId>slf4j-log4j12</artifactId> -->
27 <!--             <version>1.7.7</version> -->
28 <!--         </dependency> -->
29         <dependency>
30             <groupId>org.mybatis</groupId>
31             <artifactId>mybatis</artifactId>
32             <version>3.4.6</version>
33         </dependency>
34         <dependency>
35             <groupId>mysql</groupId>
36             <artifactId>mysql-connector-java</artifactId>
37             <version>5.1.29</version>
38         </dependency>
39     </dependencies>
40 
41 </project>

如有问题，欢迎纠正！！！

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原文地址：https://www.cnblogs.com/Charles-Yuan/p/9861099.html