前端与后端之间参数的传递与接收和@RequestBody，@Requestparam,@Param三个注解的使用

参数在前台通过对象的形式传递到后台，在后台，可以用@RequestBody注解通过Map或JSONObject接收（太麻烦，既要从Map中取值，取完值后又要封装到Map），也可以用@RequestParam注解通过具体的属性接收。在dao层可以通过Map将参数传递到mapper.xml，也可以用@Param注解将具体的属性值传递到Mapper.xml。

@RequestParam语法：

语法：@RequestParam(value=”参数名”,required=”true/false”,defaultValue=””)

1、value：参数名，

2、required：是否包含该参数，默认为true，表示该请求路径中必须包含该参数，如果不包含就报错。

示例：如果像下面这样写，当你清空（点击X号）省市区划时，会触发change事件，

<el-select v-model="listQuery.provinceCode" style="width: 160px;" placeholder="请选择省" @change="provinceChange" filterable clearable>
            <el-option v-for="item in provinceList" :key="item.id" :label="item.chiShortName"
                       :value="item.id" />
          </el-select>

provinceChange方法：

//根据省查询市
    provinceChange(value) {
      console.log(value)
      if (this.listQuery.cityCode != undefined) {
        this.listQuery.cityCode = '';
      };
      if (this.listQuery.areaCode != undefined) {
        this.listQuery.areaCode = '';
      };
      const query = { 'pid': value }
      area.selectCityByPid(query).then(response => {
        console.log(response)
        this.cityList = response.data;
      });
    },

由于pid值为空，故会报错。

@RequestMapping("/selectCity")
    public Result findAreasByPCity(@RequestParam(name = "pid") String pid) {
        return areaCodeService.findCityByPid(pid);
    }

故修改如下：

@RequestMapping("/selectCity")
    public Result findAreasByPCity(@RequestParam(name = "pid", required = false) String pid) {
        return areaCodeService.findCityByPid(pid);
    }

3、defaultValue：默认参数值，如果设置了该值，required=true将失效，自动为false,如果没有传该参数，就使用默认值

 @RequestParam(name = "page", defaultValue = "1") int pageIndex,

前端代码：

前端传递给后台一个对象。

data() {
    return { listQuery: { page: 1, limit: 20, dataCode: null, dataName: null, // enterpriseId: null, enterpriseType: null }, },

getList() {
      this.listLoading = true
      dataSet.getList(this.listQuery).then(response => {
        if (response.success) {
          this.list = response.data
          this.total = response.total
        } else {
          this.$message.error("数据集合信息获取失败")
        }
      }).catch(error => {
        console.log(error)
        this.$message.error("发生内部错误，请联系管理员")
      }).finally(() => {
        this.listLoading = false
      })
    },

getList(query) {
    return request({
      url: '/dataSet/list',
      method: 'post',
      params: query
    })
  },

后台代码：

controller：

controller用@RequestParam注解接收单个属性

@RestController
@RequestMapping("api/dataSet")
@Validated
public class DataSetController {
    private static Logger logger = LoggerFactory.getLogger(DataSetController.class);

    @Autowired
    private DataSetService dataSetService;
    @PostMapping("/list")
    public Result getDataSetList(
            @RequestParam(required = false) String dataCode,
            @RequestParam(required = false) String dataName,
            @RequestParam(name = "page", defaultValue = "1") int pageIndex,
            @RequestParam(name = "limit", defaultValue = "10") int length
    ) {
        return dataSetService.getDataSetList(dataCode, dataName, pageIndex, length);
    }
}

也可以用Map或JSONObject接收前端传递过来的整个对象

@RestController
@RequestMapping("api/dataSet")
@Validated
public class DataSetController {
    private static Logger logger = LoggerFactory.getLogger(DataSetController.class);

    @Autowired
    private DataSetService dataSetService;
    @PostMapping("/list")
    public Result getDataSetList(@RequestBody Map map ) {

　　　　　　String dataCode = (String) map.get("dataCode");
　　　　　　String dataName = (String) map.get("dataName");
　　　　　　Integer pageIndex = (Integer) map.get("pageIndex");
　　　　　　Integer length = (Integer) map.get("length");

　　　　　　return dataSetService.getDataSetList(dataCode, dataName, pageIndex, length); } }

@RestController
@RequestMapping("api/dataSet")
@Validated
public class DataSetController {
    private static Logger logger = LoggerFactory.getLogger(DataSetController.class);

    @Autowired
    private DataSetService dataSetService;
    @PostMapping("/list")
    public Result getDataSetList(@RequestBody JSONObject map ) {
　　　　　　String dataCode = map.getString("dataCode");
　　　　　　String dataName = map.getString("dataName");
　　　　　　Integer pageIndex = map.getIntValue("pageIndex");
　　　　　　Integer length = map.getIntValue("length");
　　　　　　return dataSetService.getDataSetList(dataCode, dataName, pageIndex, length); } }

service：

service中可以将参数封装到Map中再传递到dao层，即使是controller层用Map接收，service层中也要从Map中取值。

public Result getDataSetList(String dataCode, String dataName, int pageIndex, int length) {
    Map map = new HashMap();
    map.put("dataCode", dataCode);
    map.put("dataName", dataName);
    PageHelper.startPage(pageIndex, length);
    List<Map> dataSetList = dataSetMapper.selectDataSetList(map);
    PageInfo pageInfo = new PageInfo(dataSetList);
    return Result.operating("数据集合查询成功", true, Result.SUCCESS, pageInfo.getList(), (int) pageInfo.getTotal(), pageInfo.getPages());
}

service中也可以直接将参数分别传递到dao层

public Result getDataSetList(String dataCode, String dataName, int pageIndex, int length) {
    PageHelper.startPage(pageIndex, length);
    List<Map> dataSetList = dataSetMapper.selectDataSetList(dataCode,dataName);
    PageInfo pageInfo = new PageInfo(dataSetList);
    return Result.operating("数据集合查询成功", true, Result.SUCCESS, pageInfo.getList(), (int) pageInfo.getTotal(), pageInfo.getPages());
}

dao层：

如果service中将参数封装到Map中再传递到dao层，则dao层用Map

public interface DataSetMapper extends Mapper<DataSet> {
    List<Map> selectDataSetList(Map map);
}

如果service中直接将参数分别传递到dao层，则用@Param注解接收

public interface DataSetMapper extends Mapper<DataSet> {
    List<Map> selectDataSetList(@Param("dataCode") String dataCode,@Param("dataName") String dataName); }

mapper.xml:

<select id="selectDataSetList" resultType="java.util.Map">
    SELECT
    t1.id AS "dataId",
    t1.data_code AS "dataCode",
    t1.data_name AS "dataName",
    t1.remark AS "remark",
    t2.id AS "enterpriseDataSetId",
    t3.id AS "enterpriseId",
    t3.enterprise_name AS "enterpriseName"
    FROM
    sys_data_set t1
    LEFT JOIN sys_enterprise_data_set t2 ON t1.id = t2.data_id
    LEFT JOIN sys_enterprise t3 ON t2.enterprise_id = t3.id
    WHERE 1=1 AND t1.status=0
    <if test="dataCode!=null and dataCode!=''">
        AND t1.data_code LIKE '%'||#{dataCode}||'%'
    </if>
    <if test="dataName!=null and dataName!=''">
        AND t1.data_name LIKE '%'||#{dataName}||'%'
    </if>
    <if test="enterpriseId!=null and enterpriseId!=''">
        AND t3.del_flag = 0
        AND t3.id=#{enterpriseId}
    </if>
    ORDER BY t1.id DESC
</select>