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返回分页数据列表

问题描述

现服务端数据库有users表如下：



前端需要获取其分页数据列表。

实现思路

1. 接收前端参数

使用PageParam类来接收分页请求的参数。

public class PageParam {
    private int beginLine;// 当前行
    private Integer pageSize = 3;
    private Integer currentPage = 0;// 从0开始

    public int getBeginLine() {
        return pageSize * currentPage;
    }

    public Integer getPageSize() {
        return pageSize;
    }

    public void setPageSize(Integer pageSize) {
        this.pageSize = pageSize;
    }

    public Integer getCurrentPage() {
        return currentPage;
    }

    public void setCurrentPage(Integer currentPage) {
        this.currentPage = currentPage;
    }
}

进一步编写PageParam的子类UserParam。

UserParam类的作用在于，除了可以封装基本的分页请求参数外，还可以封装筛选的条件。（例如，需要获取的是userSex=”Man”的User的列表时，可以用UserParam。）

public class UserParam extends PageParam{
    private String userName;
    private String userSex;

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getUserSex() {
        return userSex;
    }

    public void setUserSex(String userSex) {
        this.userSex = userSex;
    }
}

2. 服务端处理分页请求

@RestController("/")
public class UserController {

    @Resource
    private UserMapper userMapper;
    
    @GetMapping("users")
    public BaseResult<PageResult<UserEntity>> getUserList(UserParam userParam){
        List<UserEntity> userEntityList = userMapper.getList(userParam);
        long totalNumber = userMapper.getCount(userParam);
        PageResult<UserEntity> pageResult = new PageResult<>(userParam,totalNumber,userEntityList);
        return BaseResult.successWithData(pageResult);
    }
}

注：在本例中，ORM框架为MyBatis。

服务端执行两次SQL操作，分别获取了user集合、分页请求数据的总数。

3. 将数据封装好后返回前端

然后，服务端将生成PageResult对象，再将其封装进BaseResult中返回给前端。

（代码见上面）

PageResult.java

public class PageResult<E>{
    private  int currentPage = 1;
    private long totalPage;
    private long totalNumber;
    private List<E> list;

    public PageResult(){

    }

    public PageResult(PageParam pageParam,long totalNumber,List<E> list){
        this.currentPage = pageParam.getCurrentPage();
        this.totalPage = totalNumber % pageParam.getPageSize() == 0 ? totalNumber
                / pageParam.getPageSize() : totalNumber / pageParam.getPageSize() + 1;
        this.totalNumber = totalNumber;
        this.list = list;
    }

    public int getCurrentPage() {
        return currentPage;
    }

    public void setCurrentPage(int currentPage) {
        this.currentPage = currentPage;
    }

    public long getTotalPage() {
        return totalPage;
    }

    public void setTotalPage(long totalPage) {
        this.totalPage = totalPage;
    }

    public long getTotalNumber() {
        return totalNumber;
    }

    public void setTotalNumber(long totalNumber) {
        this.totalNumber = totalNumber;
    }

    public List<E> getList() {
        return list;
    }

    public void setList(List<E> list) {
        this.list = list;
    }
}

BaseResult.java

/**
 * 通用响应对象
 */
public class BaseResult<T> {
    private static final int SUCCESS_CODE = 0;
    private static final String SUCCESS_MESSAGE = "成功";

    private int code;

    private String msg;

    private T data;
    private BaseResult(int code, String msg, T data) {
        this.code = code;
        this.msg = msg;
        this.data = data;
    }
    private BaseResult() {
        this(SUCCESS_CODE, SUCCESS_MESSAGE);
    }
    private BaseResult(int code, String msg) {
        this(code, msg, null);
    }
    private BaseResult(T data) {
        this(SUCCESS_CODE, SUCCESS_MESSAGE, data);
    }
    public static <T> BaseResult<T> success() {
        return new BaseResult<>();
    }
    public static <T> BaseResult<T> successWithData(T data) {
        return new BaseResult<>(data);
    }
    public static <T> BaseResult<T> failWithCodeAndMsg(int code, String msg) {
        return new BaseResult<>(code, msg, null);
    }
    public static <T> BaseResult<T> buildWithParam(ResponseParam param) {
        return new BaseResult<>(param.getCode(), param.getMsg(), null);
    }
    public int getCode() {
        return code;
    }
    public void setCode(int code) {
        this.code = code;
    }
    public String getMsg() {
        return msg;
    }
    public void setMsg(String msg) {
        this.msg = msg;
    }
    public T getData() {
        return data;
    }
    public void setData(T data) {
        this.data = data;
    }
    public static class ResponseParam {
        private int code;
        private String msg;
        private ResponseParam(int code, String msg) {
            this.code = code;
            this.msg = msg;
        }
        public static ResponseParam buildParam(int code, String msg) {
            return new ResponseParam(code, msg);
        }
        public int getCode() {
            return code;
        }
        public void setCode(int code) {
            this.code = code;
        }
        public String getMsg() {
            return msg;
        }
        public void setMsg(String msg) {
            this.msg = msg;
        }
    }
}

4. 测试结果

测试1

请求方式及参数：

响应结果：

注：currentPage是从0开始的。

测试2

请求方式及参数：

注：此时没有userSex的筛选条件。

响应结果：

{
    "code": 0,
    "msg": "成功",
    "data": {
        "currentPage": 0,
        "totalPage": 2,
        "totalNumber": 4,
        "list": [
            {
                "id": 4,
                "userName": "Pony",
                "passWord": "QWERTY",
                "userSex": "Man",
                "nickName": "P"
            },
            {
                "id": 3,
                "userName": "Mary",
                "passWord": "QWERTY",
                "userSex": "Man",
                "nickName": "Ma"
            },
            {
                "id": 2,
                "userName": null,
                "passWord": "QWERTY",
                "userSex": "Man",
                "nickName": "Ma"
            }
        ]
    }
}