快速入门Web开发（中）后端开发（有重点）（2）

javaCopy code@RequestMapping("/hello")
public String hello() {
  return "Hello, World!";

package com.itheima.pojo;
/**
 * 统一响应结果封装类
 */
public class Result {
    private Integer code ;//1 成功 , 0 失败
    private String msg; //提示信息
    private Object data; //数据 date
    public Result() {
    }
    public Result(Integer code, String msg, Object data) {
        this.code = code;
        this.msg = msg;
        this.data = data;
    }
    public Integer getCode() {
        return code;
    }
    public void setCode(Integer code) {
        this.code = code;
    }
    public String getMsg() {
        return msg;
    }
    public void setMsg(String msg) {
        this.msg = msg;
    }
    public Object getData() {
        return data;
    }
    public void setData(Object data) {
        this.data = data;
    }
    public static Result success(Object data){
        return new Result(1, "success", data);
    }
    public static Result success(){
        return new Result(1, "success", null);
    }
    public static Result error(String msg){
        return new Result(0, msg, null);
    }
    @Override
    public String toString() {
        return "Result{" +
                "code=" + code +
                ", msg='" + msg + '\'' +
                ", data=" + data +
                '}';
    }
}

@RequestMapping("/hello")
    public Result hello(){
        System.out.println("Hello World ~");
        //return new Result(1,"success","Hello World ~");
        return Result.success("Hello World ~");
    }

//文件寻址
 String file = this.getClass().getClassLoader().getResource("emp.xml").getFile();

package com.itheima.controller;
import com.itheima.pojo.Emp;
import com.itheima.pojo.Result;
import com.itheima.utils.XmlParserUtils;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import java.util.List;
@RestController
public class EmpController {
    @RequestMapping("/listEmp")
    public Result list(){
        //1. 加载并解析emp.xml(获取数据)
        String file = this.getClass().getClassLoader().getResource("emp.xml").getFile();
        System.out.println(file);
        List<Emp> empList = XmlParserUtils.parse(file, Emp.class);//XmlParserUtils对象用来处理xml文件
        //2. 对数据进行转换处理 - gender, job(处理数据)
        empList.stream().forEach(emp -> {//使用lambda表达式,相当于js中的箭头函数。
            //处理 gender 1: 男, 2:
            String gender = emp.getGender();//类里面
            //为什么emp没有声明为Emp类型的数据却能使用Emp类中的方法？
            //因为lambda表达式中的emp(这个位置的变量)是通过上下文来判断类型。
            //而empList是Emp类数据
            if("1".equals(gender)){
                emp.setGender("男");
            }else if("2".equals(gender)){
                emp.setGender("女");
            }
            //处理job - 1: 讲师, 2: 班主任 , 3: 就业指导
            String job = emp.getJob();
            if("1".equals(job)){
                emp.setJob("讲师");
            }else if("2".equals(job)){
                emp.setJob("班主任");
            }else if("3".equals(job)){
                emp.setJob("就业指导");
            }
        });
        //3. 响应数据
        return Result.success(empList);
    }
}

package com.itheima.pojo;
public class Emp {
    private String name;
    private Integer age;
    private String image;
    private String gender;
    private String job;
    public Emp() {
    }
    public Emp(String name, Integer age, String image, String gender, String job) {
        this.name = name;
        this.age = age;
        this.image = image;
        this.gender = gender;
        this.job = job;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Integer getAge() {
        return age;
    }
    public void setAge(Integer age) {
        this.age = age;
    }
    public String getImage() {
        return image;
    }
    public void setImage(String image) {
        this.image = image;
    }
    public String getGender() {
        return gender;
    }
    public void setGender(String gender) {
        this.gender = gender;
    }
    public String getJob() {
        return job;
    }
    public void setJob(String job) {
        this.job = job;
    }
    @Override
    public String toString() {
        return "Emp{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", image='" + image + '\'' +
                ", gender='" + gender + '\'' +
                ", job='" + job + '\'' +
                '}';
    }
}

-- if语句
select if(gender=1,'男性','女性'),count(*)
from tb_emp  group by gender  ;
-- case语句
select (case job when 1 then '班主任' when 2 then '讲师' when 3 then '学工主管' when 4 then '教研主管' else '无职位' end)
,count(*)
from tb_emp
group by job;