Mybatis入门-mapper代理Dao层开发（五）

2024-01-23 18:16:36

使用Mapper代理开发原因

1.程序员只需要写mapper接口和mapper.xml映射文件，Mybatis可以自动生成mapper接口实现类代理对象

2.只不过程序员在编写mapper接口时，需要遵循一些开发规范

mapper.java接口名跟 mapper.xml映射文件名相同并且在同一包下
在mapper.xml映射文件中，namespace=“mapper接口地址”–完全包名.mapper接口名
mapper.java接口中的方法名和mapper.xml中statement的id值一致
mapper.java接口中的方法输入参数类型和 mapper.xml中statement的parameterType指定的类型一致
mapper.java接口中的方法返回值类型和 mapper.xml中statement的resultType指定的类型一致
SqlMapConfig.xml 配置文件中 —由于使用mapper代理方式，改为加载mapper接口

目录结构

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<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/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>

<groupId>org.example</groupId>
<artifactId>MyBatisDao</artifactId>
<version>1.0-SNAPSHOT</version>

<dependencies>
<!--mybatis核心包 -->
<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.5.3</version>
</dependency>

<!--mysql驱动包 -->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>5.1.8</version>
</dependency>

<!--junit测试包 -->
<dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>4.12</version>
</dependency>

<!--日志包，方便查看动态sql语句 -->
<dependency>
    <groupId>org.slf4j</groupId>
    <artifactId>slf4j-log4j12</artifactId>
    <version>1.6.1</version>
</dependency>
</dependencies>

</project>

DeptMapper

public interface DeptMapper {
List<Dept> SelectAllDept() throws Exception;

int InsertDept(Dept dept) throws Exception;

int UpdateDept(Dept dept) throws Exception;

int DelDept(int id) throws Exception;
}

Dept

public class Dept {
private int deptno;
private String dname;
private String loc;

public int getDeptno() {
return deptno;
}

public void setDeptno(int deptno) {
this.deptno = deptno;
}

public String getDname() {
return dname;
}

public void setDname(String dname) {
this.dname = dname;
}

public String getLoc() {
return loc;
}

public void setLoc(String loc) {
this.loc = loc;
}

public Dept() {
}

public Dept(int deptno, String dname, String loc) {
this.deptno = deptno;
this.dname = dname;
this.loc = loc;
}
}

initLogRecord

public class initLogRecord {
public static void initLog() {
FileInputStream fileInputStream = null;
try {
    Properties properties = new Properties();
    fileInputStream = new FileInputStream("src/main/resources/log4j.properites");
    properties.load(fileInputStream);
    PropertyConfigurator.configure(properties);
} catch (Exception e) {
    e.printStackTrace();
} finally {
    if (fileInputStream != null) {
        try {
            fileInputStream.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}
}
}

DeptMapper

<?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填写mapper接口的全限定名-->
<mapper namespace="com.msb.mapper.DeptMapper">
<!--id要和方法名相同-->
<!--方法返回值类型 和 mapper.xml中statement的resultType指定的类型一致-->
<select id="SelectAllDept" resultType="dept">
    select * from dept
</select>
<!--方法输入参数类型 和 mapper.xml中statement的parameterType指定的类型一致-->
<insert id="InsertDept" parameterType="dept">
    insert into dept(deptno,dname,loc) values(#{deptno},#{dname},#{loc})
</insert>

<delete id="DelDept" parameterType="int">
    delete from dept where deptno = #{deptno}
</delete>

<update id="UpdateDept" parameterType="dept">
    update dept set dname = #{dname} where deptno = #{deptno}
</update>
</mapper>

JDBC.properites

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://192.168.220.130:3306/test_project?useUnicode=true&amp;characterEncoding=UTF-8
username=root
password=qwert123

log4j.properites

log4j.rootLogger=debug, stdout, R

log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout

log4j.appender.stdout.layout.ConversionPattern=%5p [%t] (%F:%L) - %m%n

log4j.appender.R=org.apache.log4j.RollingFileAppender
log4j.appender.R.File=example.log

log4j.appender.R.MaxFileSize=100KB

log4j.appender.R.MaxBackupIndex=5

log4j.appender.R.layout=org.apache.log4j.PatternLayout	
log4j.appender.R.layout.ConversionPattern=%p %t %c - %m%n

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>

<properties resource="JDBC.properites"/>

<typeAliases>
    <!--设置别名，name为当前实体类的所在位置,映射文件resultType别名为当前类名首字母小写后的名字-->
    <package name="com.msb.pojo"/>
</typeAliases>

<environments default="development">
    <environment id="development">
        <transactionManager type="JDBC"/>
        <dataSource type="POOLED">
            <property name="driver" value="${driver}"/>
            <property name="url"
                      value="${url}"/>
            <property name="username" value="${username}"/>
            <property name="password" value="${password}"/>
        </dataSource>
    </environment>
</environments>

<mappers>
    <!--接口所在的包名-->
    <package name="com.msb.mapper"/>
</mappers>
</configuration>

MybatisTest

public class MybatisTest {
private SqlSessionFactory factory;

@Before
public void init() throws IOException {
    initLogRecord.initLog();
    InputStream resource = Resources.getResourceAsStream("SqlMapConfig.xml");
    SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
    factory = builder.build(resource);
}

@Test
public void test() throws Exception {
    SqlSession sqlSession = factory.openSession();
    //传入参数为想获得接口的实现类
    DeptMapper mapper = sqlSession.getMapper(DeptMapper.class);
    List<Dept> list = mapper.SelectAllDept();
    for (Dept dept: list) {
        System.out.println(dept.getDeptno()+";"+dept.getDname()+";"+dept.getLoc());
    }
}
}

运行结果

码农公寓

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