Mybatis Plus Join使用方法示例详解_Java

1、pom文件

不引入mybatis的任何内容，防止包冲突

<dependency>
			<groupid>com.baomidou</groupid>
			<artifactid>mybatis-plus-boot-starter</artifactid>
			<version>3.5.5</version>
		</dependency>
		<dependency>
			<groupid>com.github.yulichang</groupid>
			<artifactid>mybatis-plus-join-boot-starter</artifactid>
			<version>1.5.3</version>
		</dependency>

2、yaml配置文件

mybatis-plus-join:
    #是否打印 mybatis plus join banner 默认true
    banner: true
    #全局启用副表逻辑删除(默认true) 关闭后关联查询不会加副表逻辑删除
    sub-table-logic: true
    #拦截器mappedstatement缓存(默认true)
    ms-cache: true
    #表别名(默认 t)
    table-alias: t
    #副表逻辑删除条件的位置，支持where、on
    #默认on （1.4.7.2及之前版本默认为where）
    logic-del-type: on

3、分页插件

 
import com.baomidou.mybatisplus.annotation.dbtype;
import com.baomidou.mybatisplus.extension.plugins.mybatisplusinterceptor;
import com.baomidou.mybatisplus.extension.plugins.inner.paginationinnerinterceptor;
import org.springframework.context.annotation.bean;
import org.springframework.context.annotation.configuration;
/**
 * mybatis-plus配置
 *
 * @author mark sunlightcs@gmail.com
 */
@configuration
public class mybatisplusconfig {
    /**
     * 添加分页插件
     */
    @bean
    public mybatisplusinterceptor mybatisplusinterceptor() {
        mybatisplusinterceptor interceptor = new mybatisplusinterceptor();
        interceptor.addinnerinterceptor(new paginationinnerinterceptor(dbtype.mysql)); // 如果配置多个插件, 切记分页最后添加
        // 如果有多数据源可以不配具体类型, 否则都建议配上具体的 dbtype
        return interceptor;
    }
}

4、示例代码：

 
import com.baomidou.mybatisplus.annotation.tableid;
import com.baomidou.mybatisplus.annotation.tablename;
import lombok.data;
@data
@tablename("address")
public class address {
    @tableid
    private long id;
    private long userid;
    private string city;
    private string address;
}
import com.baomidou.mybatisplus.annotation.tableid;
import com.baomidou.mybatisplus.annotation.tablename;
import lombok.data;
@data
@tablename("user")
public class user {
    @tableid
    private long id;
    private string name;
    private integer age;
    private string email;
}
import lombok.data;
import lombok.tostring;
@data
@tostring
public class userdto {
    private long id;
    private string name;
    private integer age;
    private string email;
    private string city;
    private string address;
}
import com.github.yulichang.base.mpjbasemapper;
import org.apache.ibatis.annotations.mapper;
@mapper
public interface addressmapper extends mpjbasemapper<address> {
}
import com.github.yulichang.base.mpjbasemapper;
import org.apache.ibatis.annotations.mapper;
@mapper
public interface usermapper extends mpjbasemapper<user> {
}

5、测试代码

 
import cn.hutool.json.jsonutil;
import com.baomidou.mybatisplus.extension.plugins.pagination.page;
import com.github.yulichang.wrapper.mpjlambdawrapper;
import lombok.extern.slf4j.slf4j;
import org.junit.test;
import org.junit.runner.runwith;
import org.springframework.beans.factory.annotation.autowired;
import org.springframework.boot.test.context.springboottest;
import org.springframework.test.context.junit4.springrunner;
import java.util.list;
@springboottest(classes = renrenapplication.class)
@runwith(springrunner.class)
@slf4j
public class sampletest {
    @autowired
    private usermapper usermapper;
    @test
    public void testselect() {
        mpjlambdawrapper<user> wrapper = new mpjlambdawrapper<user>()
                .selectall(user.class)//查询user表全部字段
                .select(address::getcity, address::getaddress)
                .leftjoin(address.class, address::getuserid, user::getid);
        list<userdto> userlist = usermapper.selectjoinlist(userdto.class, wrapper);
        userlist.foreach(system.out::println);
        //分页查询 （需要启用 mybatis plus 分页插件）
        page<userdto> listpage = usermapper.selectjoinpage(new page<>(1, 2), userdto.class, wrapper);
        log.info("分页查询结果：{}", jsonutil.tojsonstr(listpage));
    }
}

class test {
    @resource
    private usermapper usermapper;
    void testjoin() {
        //和mybatis plus一致，mpjlambdawrapper的泛型必须是主表的泛型，并且要用主表的mapper来调用
        mpjlambdawrapper<userdo> wrapper = joinwrappers.lambda(userdo.class)
                .selectall(userdo.class)//查询user表全部字段
                .select(useraddressdo::gettel)//查询user_address tel 字段
                .selectas(useraddressdo::getaddress, userdto::getuseraddress)//别名
                .select(areado::getprovince, areado::getcity)
                .leftjoin(useraddressdo.class, useraddressdo::getuserid, userdo::getid)
                .leftjoin(areado.class, areado::getid, useraddressdo::getareaid)
                .eq(userdo::getid, 1)
                .like(useraddressdo::gettel, "1")
                .gt(userdo::getid, 5);
        //连表查询 返回自定义resulttype
        list<userdto> list = usermapper.selectjoinlist(userdto.class, wrapper);
        //分页查询 （需要启用 mybatis plus 分页插件）
        page<userdto> listpage = usermapper.selectjoinpage(new page<>(2, 10), userdto.class, wrapper);
    }
}

6、和pagehelper结合

6.1引入pom文件

        <dependency>
			<groupid>com.baomidou</groupid>
			<artifactid>mybatis-plus-boot-starter</artifactid>
			<version>3.5.5</version>
		</dependency>
		<dependency>
			<groupid>com.github.yulichang</groupid>
			<artifactid>mybatis-plus-join-boot-starter</artifactid>
			<version>1.5.3</version>
		</dependency>
		<dependency>
			<groupid>com.github.pagehelper</groupid>
			<artifactid>pagehelper-spring-boot-starter</artifactid>
			<version>1.4.6</version>
		</dependency>

6.2 pagehelper配置

pagehelper:
    helper-dialect: mysql    # 数据库方言
    reasonable: true         # 页码越界时自动修正
    support-methods-arguments: true  # 支持接口参数分页
    params: count=countsql

6.3 测试代码：

 
import lombok.extern.slf4j.slf4j;
import org.junit.test;
import org.junit.runner.runwith;
import org.springframework.beans.factory.annotation.autowired;
import org.springframework.boot.test.context.springboottest;
import org.springframework.test.context.junit4.springrunner;
import java.util.list;
@springboottest(classes = application.class)
@runwith(springrunner.class)
@slf4j
public class sampletest {
    @autowired
    private usermapper usermapper;
    @test
    public void testselect() {
        mpjlambdawrapper<user> wrapper = new mpjlambdawrapper<user>()
                .selectall(user.class)//查询user表全部字段
                .select(address::getcity, address::getaddress)
                .leftjoin(address.class, address::getuserid, user::getid);
        list<userdto> userlist = usermapper.selectjoinlist(userdto.class, wrapper);
        log.info("查询结果：{}", jsonutil.tojsonstr(userlist));
        pagehelper.startpage(1, 2);
        list<userdto> userlist1 = usermapper.selectjoinlist(userdto.class, wrapper);
        pageinfo<userdto> pageinfo = new pageinfo<>(userlist1);
        log.info("pagehelper 分页查询结果：{}", jsonutil.tojsonstr(pageinfo));
        pagehelper.clearpage();
        //分页查询 （需要启用 mybatis plus 分页插件）
        page<userdto> listpage = usermapper.selectjoinpage(new page<>(1, 4), userdto.class, wrapper);
        log.info("分页查询结果：{}", jsonutil.tojsonstr(listpage));
    }
}

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