获取子父节点，tree树状结构的方式--通过循环的方式

1.导包

<dependencies>　　//将domain quary写到了这层    <dependency>        <groupId>cn.xxx.aigou</groupId>        <artifactId>qqq_product_interface</artifactId>        <version>1.0-SNAPSHOT</version>    </dependency>

        <!--springboot相关的依赖-->        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-web</artifactId>        </dependency>

        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-test</artifactId>        </dependency>

        <!--mp的依赖-->        <dependency>            <groupId>com.baomidou</groupId>            <artifactId>mybatis-plus-boot-starter</artifactId>            <version>2.2.0</version>        </dependency>

        <dependency>            <groupId>mysql</groupId>            <artifactId>mysql-connector-java</artifactId>            <version>5.1.20</version>        </dependency>    <!--eureka的客户端-->    <dependency>        <groupId>org.springframework.cloud</groupId>        <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>    </dependency>

    <!--swagger2接口文档依赖-->    <dependency>        <groupId>io.springfox</groupId>        <artifactId>springfox-swagger2</artifactId>        <version>2.9.2</version>    </dependency>    <!-- https://mvnrepository.com/artifact/io.springfox/springfox-swagger-ui -->    <dependency>        <groupId>io.springfox</groupId>        <artifactId>springfox-swagger-ui</artifactId>        <version>2.9.2</version>    </dependency>    <!--配置中心支持-->    <dependency>        <groupId>org.springframework.cloud</groupId>        <artifactId>spring-cloud-starter-config</artifactId>    </dependency></dependencies>

2.contrlloer实现

/** * 树状结构数据查询： * @return */@RequestMapping(value = "/treeData",method = RequestMethod.GET)public List<ProductType> treeData(){

    return productTypeService.treeData();}

3.service写逻辑

@Overridepublic List<ProductType> treeData() {    /*        使用循环的方式获取不同层次的节点     */    return treeDataLoop();}private List<ProductType> treeDataLoop() {    //1：首先查询出所有的数据    List<ProductType> allProductTypes = productTypeMapper.selectList(null);

    //获取所有的数据的key--value的值    Map<Long,ProductType> map=new HashMap<>();    for (ProductType pt : allProductTypes) {        map.put(pt.getId(),pt);    }

    //最终返回的结果：一级菜单    List<ProductType> result=new ArrayList<>();

    //2：遍历：封装父节点和子节点    for (ProductType currentProductType : allProductTypes) {        //判断是否是一级菜单        if(currentProductType.getPid()==0){            // 如果是一级菜单则返回            result.add(currentProductType);        }else{            ProductType parent =map.get(currentProductType.getPid());            parent.getChildren().add(currentProductType);        }

    }

    return result;}

3.前台写好后，直接测试

原文地址：https://www.cnblogs.com/wgyi140724-/p/10634135.html