mapper xml的if標簽使用

開發工具:idea

版本工具:maven

1.pom.xml

<dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>

    <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
    <dependency>
      <groupId>org.mybatis</groupId>
      <artifactId>mybatis</artifactId>
      <version>3.3.0</version>
    </dependency>

    <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>8.0.16</version>
    </dependency>

      <!--日志需要-->
      <dependency>
          <groupId>log4j</groupId>
          <artifactId>log4j</artifactId>
          <version>1.2.17</version>
      </dependency>
      <dependency>
          <groupId>org.slf4j</groupId>
          <artifactId>slf4j-api</artifactId>
          <version>1.7.30</version>
      </dependency>
      <dependency>
          <groupId>org.slf4j</groupId>
          <artifactId>slf4j-log4j12</artifactId>
          <version>1.7.7</version>
      </dependency>

2.Role.java

package com.lenovo.pojo;

public class Role {

    private Long id;//主鍵
    private String roleName;//角色名稱
    private String note;//備注

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getRoleName() {
        return roleName;
    }

    public void setRoleName(String roleName) {
        this.roleName = roleName;
    }

    public String getNote() {
        return note;
    }

    public void setNote(String note) {
        this.note = note;
    }

    @Override
    public String toString() {
        return "Role{" +
                "id=" + id +
                ", roleName='" + roleName + '\'' +
                ", note='" + note + '\'' +
                '}';
    }
}

3.RoleMapper.java

package com.lenovo.dao;

import com.lenovo.pojo.Role;
import org.apache.ibatis.annotations.Param;

public interface RoleMapper {

    //查詢單個角色
    public Role findRole(@Param("roleName") String roleName);

}

4.SqlSessionFactoryUtil.java

package com.lenovo.util;

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 java.io.IOException;
import java.io.InputStream;

public class SqlSessionFactoryUtil {

    //SqlSessionFactory對象
    private static SqlSessionFactory sqlSessionFactory = null;
    //類線程鎖
    private static final Class CLASS_LOCK = SqlSessionFactoryUtil.class;

    //私有化構造函數
    private SqlSessionFactoryUtil(){};

    //構建SqlSessionFactory
    public static SqlSessionFactory initSqlSessionFactory(){
        String resource = "mybatis-config.xml";
        InputStream inputStream = null;
        try {
            inputStream = Resources.getResourceAsStream(resource);
        } catch (IOException e) {
            e.printStackTrace();
        }

        synchronized (CLASS_LOCK){
            if (sqlSessionFactory == null){
                sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
            }
        }
        return sqlSessionFactory;
    }

    //打開SqlSession
    public static SqlSession openSqlSession(){
        if (sqlSessionFactory == null){
            initSqlSessionFactory();
        }
        return sqlSessionFactory.openSession();
    }

}

5.RoleMapper.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="com.lenovo.dao.RoleMapper">
    
    <resultMap id="roleResultMap" type="com.lenovo.pojo.Role">
        <id property="id" column="id" javaType="Long" jdbcType="BIGINT"/>
        <result property="roleName" column="role_name" javaType="String" jdbcType="VARCHAR"/>
        <result property="note" column="note" javaType="String" jdbcType="VARCHAR"/>
    </resultMap>

    <select id="findRole" parameterType="string" resultMap="roleResultMap">
        select id,role_name,note from t_role where 1=1
        <if test="roleName != null and roleName != ''">
            and role_name like concat('%', #{roleName}, '%')
        </if>
    </select>
</mapper>

6.jdbc.properties

#數據庫配置文件
driver=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/mysql?serverTimezone=Asia/Shanghai&useUnicode=true&characterEncoding=UTF-8&zeroDateTimeBehavior=convertToNull&useSSL=false
username=root
password=root

7.log4j.properties

log4j.rootLogger=DEBUG,stdout
log4j.logger.org.mybatis=DEBUG
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p %d %C: %m%n

8.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">
<!--test1練習使用的mybatis核心配置文件-->
<configuration>
    <!-- 定義別名 -->
    <typeAliases>
        <!--定義別名role,代表了com.lenovo.test1.pojo.Role,這樣我們就可以在Mybatis上下文中引用它了-->
        <typeAlias type="com.lenovo.pojo.Role" alias="role"/>
    </typeAliases>

    <!--定義數據庫信息，默認使用development數據庫構建環境-->
    <environments default="development">
        <environment id="development">
            <!--采用jdbc事務管理-->
            <transactionManager type="JDBC"/>
            <!--配置數據庫鏈接信息-->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mysql?serverTimezone=Asia/Shanghai&amp;useUnicode=true&amp;characterEncoding=UTF-8&amp;zeroDateTimeBehavior=convertToNull&amp;useSSL=false"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>

    <!--配置映射器，這里引入了一個xml,它的作用是提供SQL和SQL對POJO的映射規則定義，它包含了映射器里面的信息。mybatis將解析這個xml，來為我們生成映射器-->
    <mappers>
        <mapper resource="mapper\RoleMapper.xml" />
    </mappers>
</configuration>

9.MybatisExample.java

package com.lenovo;

import com.lenovo.dao.RoleMapper;
import com.lenovo.pojo.Role;
import com.lenovo.util.SqlSessionFactoryUtil;
import org.apache.ibatis.session.SqlSession;

/**
 * select標簽中的if標簽測試
 */
public class MybatisExample {

    public static void main(String[] args) {
        SqlSession sqlSession = SqlSessionFactoryUtil.initSqlSessionFactory().openSession();
        RoleMapper roleMapper = sqlSession.getMapper(RoleMapper.class);
        Role role = roleMapper.findRole("zhang");
        System.out.println("角色信息" + role.toString());
    }

}