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使用AOP+反射实现自定义Mybatis多表关联查询

作者：sushengbuyu

这篇文章主要介绍了使用AOP+反射实现自定义Mybatis多表关联,目前的需求是增强现有的查询，使用简单的注解即可实现多表关联，本文通过实例代码给大家介绍的非常详细，需要的朋友可以参考下

一、需求

目前使用的ORM框架是Mybatis Plus，是Mybatis的增强框架，基础的CRUD的方法都集成了，开发起来很是方便。但是项目中总是需要多表关联查询。

Mybatis的多表关联有两种

一、在Mapper中使用@Result @One @Many注解

二、在xml文件中配置对应的resultMap和关联标签

使用起来很不方便。JPA倒是有多表关联的注解实现，但是不想再引入另一个ORM框架。

目前的需求是增强现有的查询，使用简单的注解即可实现多表关联。

二、核心代码

GitHub：https://github.com/sushengbuyu/mybatis-mapping-demo

实现该功能总共需要四个文件

两个自定义注解，一个虚拟Mapper，一个切面处理类

源码

MapTo

自定义映射注解，标注需要映射处理的字段

import java.lang.annotation.*;
/**
 * @author victor
 * @desc 自定义多表关联映射注解
 * @date 2022/5/23
 */
@Documented
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface MapTo {
    /**
     * 映射目标
     */
    Class<?> targetClass();

    /**
     * 执行SQL
     */
    String sql();

    /**
     * 嵌套处理
     * 为true时，如果映射的对象类中有映射字段，也执行映射操作
     */
    boolean doDeep() default false;
}

DoMap

自定义映射处理注解，标注需要执行映射的方法

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
 * @author victor
 * @desc 标注该需要执行映射处理的方法
 * @date 2022/5/23
 */
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface DoMap {
    /**
     * 需要处理映射的类
     * @return Class
     */
    Class<?> targetClass();

    /**
     * spel表达式
     * 默认为空
     * @return String
     */
    String spel() default "";
}

IDualMapper

虚拟Mapper，用来执行自定义SQL

import java.util.List;
import java.util.Map;
/**
 * @author victor
 * @desc 虚拟Mapper
 * @date 2022/5/23
 */
@Mapper
public interface IDualMapper {

    /**
     * 执行自定义SQL
     * @param sql sql
     * @return List<Map<String, Object>>
     */
    List<Map<String, Object>> executeSql(String sql);
}

DualMapper

使用者自行实现DualMapper，解除mybatis强依赖

package sushengbuyu.maptodemo.sys.mapper;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;
import sushengbuyu.maptodemo.aop.IDualMapper;
import java.util.List;
import java.util.Map;
/**
 * @author victor
 * @desc 虚拟Mapper
 * @date 2022/5/23
 */
@Mapper
public interface DualMapper extends IDualMapper {
    /**
     * 执行自定义SQL
     * @param sql sql
     * @return List<Map<String, Object>>
     */
    @Select("${sql}")
    List<Map<String, Object>> executeSql(@Param("sql") String sql);
}

DoMapAspect

切面处理类，核心代码，执行映射操作

package sushengbuyu.maptodemo.aop;
import cn.hutool.core.bean.BeanUtil;
import cn.hutool.core.util.ClassUtil;
import cn.hutool.core.util.ReUtil;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Pointcut;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.expression.Expression;
import org.springframework.expression.ExpressionParser;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.stereotype.Component;
import org.springframework.util.StringUtils;
import javax.annotation.PostConstruct;
import java.lang.reflect.Field;
import java.util.*;
import java.util.stream.Collectors;
/**
 * @author victor
 * @desc 自定义关联映射切面
 * @date 2022/5/23
 */
@Component
@Aspect
public class DoMapAspect {
    private final static Logger log = LoggerFactory.getLogger(DoMapAspect.class);
    /**
     * 保存MapTo映射关系
     * key 映射字段所在类
     * value 映射字段集合
     */
    private static final Map<Class<?>, Set<String>> MAPPING = new HashMap<>(8);
    private final IDualMapper dualMapper;
    public DoMapAspect(DualMapper dualMapper) {
        this.dualMapper = dualMapper;
    }
    /**
     * 初始化映射关系
     * 扫描指定包下所有类，找出带有MapTo注解的字段
     * 存储映射数据
     */
    @PostConstruct
    public void initMap() {
        // 初始化所有MapTo对象
        // 扫描所有类
        Set<Class<?>> classes = ClassUtil.scanPackage("sushengbuyu.maptodemo");
        int totalField = 0;
        // 找出使用MapTo注解的对象
        for (Class<?> c : classes) {
            Field[] fields = c.getDeclaredFields();
            for (Field f : fields) {
                if (null != f.getAnnotation(MapTo.class)){
                    log.info("找到需要映射的字段: 类名：{} - 字段名：{}", c.getName(), f.getName());
                    // 保存映射关系
                    Set<String> set;
                    if (MAPPING.containsKey(c)) {
                        set = MAPPING.get(c);
                    } else {
                        set = new HashSet<>();
                    }
                    set.add(f.getName());
                    MAPPING.put(c, set);
                    totalField++;
                }
            }
        }
        log.info("总计{}个映射类，{}个映射字段", MAPPING.size(), totalField);
    }
    /**
     * 切点
     * @param doMap 执行映射注解
     */
    @Pointcut("@annotation(doMap)")
    public void point(DoMap doMap){}
    /**
     * 处理关联映射
     * @param point 切点
     * @param doMap 映射处理配置
     * @return Object
     * @throws Throwable 异常
     */
    @Around(value = "@annotation(doMap)")
    public Object doMap(ProceedingJoinPoint point, DoMap doMap) throws Throwable {
        // 执行切面方法
        Object obj = point.proceed();
        try {
            Object relObj = obj;
            if (StringUtils.hasLength(doMap.spel())) {
                // 如果使用了SPEL表达式，则从返回值中获取处理对象
                ExpressionParser parser = new SpelExpressionParser();
                Expression expression = parser.parseExpression(doMap.spel());
                relObj = expression.getValue(obj);
            }
            // 获取映射类
            Class<?> c = doMap.targetClass();
            // 映射处理
            doMapping(c, relObj);
        } catch (Exception e) {
            log.error("映射异常", e);
        }
        log.info("返回对象：{}", obj);
        return obj;
    }
    private void doMapping(Class<?> c, Object obj) throws Exception {
        if (obj instanceof Collection) {
            // 集合
            Collection<?> co = (Collection<?>) obj;
            for (Object o : co) {
                mapping(c, o);
            }
        } else {
            // 单个对象
            mapping(c, obj);
        }
    }
    private void mapping(Class<?> c, Object obj) throws Exception {
        // 判断是否有映射关系
        if (MAPPING.containsKey(c)) {
            log.info("处理映射类：{}", c.getName());
            // 从缓存中获取映射字段名称
            Set<String> filedNames = MAPPING.get(c);
            for (String fieldName : filedNames) {
                Field f = c.getDeclaredField(fieldName);
                log.info("处理映射字段：{}", f.getName());
                // 获取映射注解
                MapTo mapTo = f.getAnnotation(MapTo.class);
                log.info("映射配置：{}", mapTo);
                // 设置私有字段访问权限
                f.setAccessible(true);
                // 执行SQL
                String sql = mapTo.sql();
                // 处理SQL变量
                List<String> res = ReUtil.findAll("\$\{(.*?)}", sql, 0);
                log.info("SQL变量：{}", res);
                for (String re : res) {
                    Field ff = obj.getClass().getDeclaredField(re.substring(2, re.length()-1));
                    ff.setAccessible(true);
                    Object o = ff.get(obj);
                    sql = sql.replace(re, o.toString());
                }
                log.info("最终SQL：{}", sql);
                List<Map<String, Object>> results = dualMapper.executeSql(sql);
                Object v = null;
                if (Collection.class.isAssignableFrom(f.getType())) {
                    // 集合对象
                    if (results.size() > 0) {
                        v = results.stream()
                                .map(r -> mapToBean(r, mapTo.targetClass()))
                                .collect(Collectors.toList());
                    }
                } else {
                    // 单个对象
                    if (results.size() > 1) {
                        log.error("预计返回一条数据，实际返回多条数据。执行SQL: {}", sql);
                    } else if (results.size() == 1) {
                        // 转换结果，赋值
                        v = mapToBean(results.get(0), mapTo.targetClass());
                    }
                }
                if (v != null && mapTo.doDeep()) {
                    doMapping(mapTo.targetClass(), v);
                }
                f.set(obj, v);
            }
        }
    }
    /**
     * Map对象转Bean
     * @param map map
     * @param clazz bean
     * @return bean
     */
    private Object mapToBean(Map<?, ?> map, Class<?> clazz) {
        try {
            return BeanUtil.fillBeanWithMap(map, clazz.newInstance(), true);
        } catch (InstantiationException | IllegalAccessException e) {
            log.error("实例化异常", e);
            return null;
        }
    }
}

三、使用方法

测试类

SysUser

import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableId;
import java.io.Serializable;
import java.util.List;
import java.util.StringJoiner;
/**
 * @author victor
 * @desc 系统用户
 * @date 2022/5/17
 */
public class SysUser implements Serializable {
    private static final long serialVersionUID = 4855472141572371097L;
    @TableId(type = IdType.ASSIGN_ID)
    private Long id;
    /**
     * 登录用户名
     */
    private String username;
    /**
     * 登录密码
     */
    private String password;
    /**
     * 昵称
     */
    private String nickName;
    
    @MapTo(targetClass = SysRole.class
            , doDeep = true
            , sql = "SELECT * FROM sys_role WHERE user_id=${id}")
    @TableField(exist = false)
    private SysRole sysRole;
    @MapTo(targetClass = SysRole.class
            , doDeep = true
            , sql = "SELECT * FROM sys_role WHERE user_id=${id}")
    @TableField(exist = false)
    private List<SysRole> roleList;

    public Long getId() {
        return id;
    }
    public void setId(Long id) {
        this.id = id;
    }
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    public String getNickName() {
        return nickName;
    }
    public void setNickName(String nickName) {
        this.nickName = nickName;
    }
    public SysRole getSysRole() {
        return sysRole;
    }
    public void setSysRole(SysRole sysRole) {
        this.sysRole = sysRole;
    }
    public List<SysRole> getRoleList() {
        return roleList;
    }
    public void setRoleList(List<SysRole> roleList) {
        this.roleList = roleList;
    }
    @Override
    public String toString() {
        return new StringJoiner(", ", SysUser.class.getSimpleName() + "[", "]")
                .add("id=" + id)
                .add("username='" + username + "'")
                .add("password='" + password + "'")
                .add("nickName='" + nickName + "'")
                .add("sysRole=" + sysRole)
                .add("roleList=" + roleList)
                .toString();
    }
}

SysRole

package sushengbuyu.maptodemo.sys.po;
import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableId;
import sushengbuyu.maptodemo.aop.MapTo;
import java.util.List;
import java.util.StringJoiner;
/**
 * @author victor
 * @desc 说明
 * @date 2022/5/23
 */
public class SysRole {
    @TableId
    private Long id;
    private Long userId;
    private String name;
    @MapTo(targetClass = SysPermission.class
            , sql = "SELECT p.* FROM sys_permission p " +
            "LEFT JOIN sys_role_permission rp ON p.id = rp.perm_id " +
            "WHERE rp.role_id = ${id}")
    @TableField(exist = false)
    private List<SysPermission> permissionList;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Long getId() {
        return id;
    }
    public void setId(Long id) {
        this.id = id;
    }
    public Long getUserId() {
        return userId;
    }
    public void setUserId(Long userId) {
        this.userId = userId;
    }
    public List<SysPermission> getPermissionList() {
        return permissionList;
    }
    public void setPermissionList(List<SysPermission> permissionList) {
        this.permissionList = permissionList;
    }
    @Override
    public String toString() {
        return new StringJoiner(", ", SysRole.class.getSimpleName() + "[", "]")
                .add("id=" + id)
                .add("userId=" + userId)
                .add("name='" + name + "'")
                .toString();
    }
}

SysPermission

package sushengbuyu.maptodemo.sys.po;
import java.util.StringJoiner;
/**
 * @author victor
 * @desc 说明
 * @date 2022/5/25
 */
public class SysPermission {
    private Long id;
    private String name;
    private Integer type;
    public Long getId() {
        return id;
    }
    public void setId(Long id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Integer getType() {
        return type;
    }
    public void setType(Integer type) {
        this.type = type;
    }
    @Override
    public String toString() {
        return new StringJoiner(", ", SysPermission.class.getSimpleName() + "[", "]")
                .add("id=" + id)
                .add("name='" + name + "'")
                .add("type=" + type)
                .toString();
    }
}

SysUserService

测试用例就常见的三种, 查单个，查列表，查分页

import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import org.springframework.stereotype.Service;
import java.io.Serializable;
import java.util.List;
/**
 * @author victor
 * @desc 说明
 * @date 2022/5/17
 */
@Service
public class SysUserService extends ServiceImpl<SysUserMapper, SysUser> {
    @DoMap(targetClass = SysUser.class)
    @Override
    public SysUser getById(Serializable id) {
        return super.getById(id);
    }
    @DoMap(targetClass = SysUser.class)
    public List<SysUser> listAll() {
        QueryWrapper<SysUser> wrapper = new QueryWrapper<>();
        return baseMapper.selectList(wrapper);
    }
    /**
     * 从Page中取records作为处理对象
     */
    @DoMap(targetClass = SysUser.class, spel = "records")
    public Page<SysUser> page() {
        QueryWrapper<SysUser> wrapper = new QueryWrapper<>();
        Page<SysUser> p = new Page<>(1, 10);
        return baseMapper.selectPage(p, wrapper);
    }
}

DoMapTests

import cn.hutool.json.JSONUtil;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
//@RunWith(SpringRunner.class)
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
class DoMapTests {
    @Autowired
    private SysUserService service;
    @Test
    void single() {
        System.out.println(JSONUtil.toJsonPrettyStr(service.getById(1)));
    }
    @Test
    void list() {
        System.out.println(JSONUtil.toJsonPrettyStr(service.listAll()));
    }
    @Test
    void page() {
        System.out.println(JSONUtil.toJsonPrettyStr(service.page()));
    }
}

测试数据

测试结果

single

{
    "nickName": "aa11",
    "roleList": [
        {
            "permissionList": [
                {
                    "type": 0,
                    "name": "add",
                    "id": 1
                },
                {
                    "type": 0,
                    "name": "query",
                    "id": 2
                }
            ],
            "userId": 1,
            "name": "r1",
            "id": 11
        },
        {
            "permissionList": [
                {
                    "type": 0,
                    "name": "del",
                    "id": 3
                }
            ],
            "userId": 1,
            "name": "r2",
            "id": 12
        }
    ],
    "password": "123456",
    "id": 1,
    "username": "a1"
}

list

[
    {
        "nickName": "aa11",
        "roleList": [
            {
                "permissionList": [
                    {
                        "type": 0,
                        "name": "add",
                        "id": 1
                    },
                    {
                        "type": 0,
                        "name": "query",
                        "id": 2
                    }
                ],
                "userId": 1,
                "name": "r1",
                "id": 11
            },
            {
                "permissionList": [
                    {
                        "type": 0,
                        "name": "del",
                        "id": 3
                    }
                ],
                "userId": 1,
                "name": "r2",
                "id": 12
            }
        ],
        "password": "123456",
        "id": 1,
        "username": "a1"
    },
    {
        "sysRole": {
            "userId": 2,
            "name": "r3",
            "id": 13
        },
        "nickName": "aa22",
        "roleList": [
            {
                "userId": 2,
                "name": "r3",
                "id": 13
            }
        ],
        "password": "123456",
        "id": 2,
        "username": "a2"
    }
]

page

{
    "optimizeCountSql": true,
    "records": [
        {
            "nickName": "aa11",
            "roleList": [
                {
                    "permissionList": [
                        {
                            "type": 0,
                            "name": "add",
                            "id": 1
                        },
                        {
                            "type": 0,
                            "name": "query",
                            "id": 2
                        }
                    ],
                    "userId": 1,
                    "name": "r1",
                    "id": 11
                },
                {
                    "permissionList": [
                        {
                            "type": 0,
                            "name": "del",
                            "id": 3
                        }
                    ],
                    "userId": 1,
                    "name": "r2",
                    "id": 12
                }
            ],
            "password": "123456",
            "id": 1,
            "username": "a1"
        },
        {
            "sysRole": {
                "userId": 2,
                "name": "r3",
                "id": 13
            },
            "nickName": "aa22",
            "roleList": [
                {
                    "userId": 2,
                    "name": "r3",
                    "id": 13
                }
            ],
            "password": "123456",
            "id": 2,
            "username": "a2"
        }
    ],
    "searchCount": true,
    "total": 0,
    "current": 1,
    "size": 10,
    "orders": [
    ]
}

到此这篇关于使用AOP+反射实现自定义Mybatis多表关联的文章就介绍到这了,更多相关Mybatis多表关联内容请搜索脚本之家以前的文章或继续浏览下面的相关文章希望大家以后多多支持脚本之家！

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