利用SpringBoot实现RestFul风格的增删改查操作

会遇到的问题：1、在提交delete请求时，可能会报405错误，解决办法在配置文件中加入在配置文件中加入spring.mvc.hiddenmethod.filter.enabled=true启用隐藏方法过滤器

　　　　　2、可能会遇到Error creating bean with name ‘requestMappingHandlerMapping‘ defined in class path resource ，解决办法：自己检查controller的请求头是不是有重复的

说明：这个小项目没有使用数据库，利用map容器模拟了几条数据。我是在b站上学习了尚硅谷的SpringBoot教程。

开搞~！！！

我的环境（idea 2019.3.3、maven3.6）

准备工作：

一、准备好静态页面（bootstrap中文网很多）

二、创建一个SpringBoot工程，加入Web、Thymeleaf依赖。

三、引入静态资源，页面放在templates文件夹下，*.js、*.css和图片放在static文件夹下

四、修改页面，因为使用了Thymeleaf模板引擎，为了保证正常使用时有提示，在页面html标签中加入

xmlns:th="http://www.thymeleaf.org"

修改静态资源的超链接格式举例：

<link th:href="@{/asserts/css/bootstrap.min.css}"  rel="stylesheet">

根据自己下载的页面选择是否抽取公共页面，thymeleaf抽取页面的三种格式

th:insert：将公共片段整个插入到声明引入的元素中，带div标签

th:replace：将声明引入的元素替换为公共片段，不带div标签

th:include：将被引入的片段的内容包含进这个标签中，带div标签但是不带公共片段的标签头，也就是直接将内容放进一个div中

<footer th:fragment="copy">
&copy; 2011 The Good Thymes Virtual Grocery
</footer>

引入方式
<div th:insert="footer :: copy"></div>
<div th:replace="footer :: copy"></div>
<div th:include="footer :: copy"></div>

效果
<div>
    <footer>
    &copy; 2011 The Good Thymes Virtual Grocery
    </footer>
</div>

<footer>
&copy; 2011 The Good Thymes Virtual Grocery
</footer>

<div>
&copy; 2011 The Good Thymes Virtual Grocery
</div>

五、准备实体类、持久层接口（本项目业务简单，暂时不加业务层）

Employee实体类（构造器、gette/setter方法省略）

　　 private Integer id;
    private String lastName;

    private String email;
    //1 男, 0 女
    private Integer gender;
    private Department department;
    private Date birth;

Department实体类

private Integer id;
    private String departmentName;

EmployeeDao接口

@Repository
public class EmployeeDao {

    private static Map<Integer, Employee> employees = null;
    
    @Autowired
    private DepartmentDao departmentDao;
    
    static{
        employees = new HashMap<Integer, Employee>();

        employees.put(1001, new Employee(1001, "E-AA", "", 1, new Department(101, "D-AA")));
        employees.put(1002, new Employee(1002, "E-BB", "", 1, new Department(102, "D-BB")));
        employees.put(1003, new Employee(1003, "E-CC", "", 0, new Department(103, "D-CC")));
        employees.put(1004, new Employee(1004, "E-DD", "", 0, new Department(104, "D-DD")));
        employees.put(1005, new Employee(1005, "E-EE", "", 1, new Department(105, "D-EE")));
    }
    
    private static Integer initId = 1006;
    
    public void save(Employee employee){
        if(employee.getId() == null){
            employee.setId(initId++);
        }
        
        employee.setDepartment(departmentDao.getDepartment(employee.getDepartment().getId()));
        employees.put(employee.getId(), employee);
    }
    
    public Collection<Employee> getAll(){
        return employees.values();
    }
    
    public Employee get(Integer id){
        return employees.get(id);
    }
    
    public void delete(Integer id){
        employees.remove(id);
    }
}

DepartmentDao

@Repository
public class DepartmentDao {

    private static Map<Integer, Department> departments = null;
    
    static{
        departments = new HashMap<Integer, Department>();
        
        departments.put(101, new Department(101, "D-AA"));
        departments.put(102, new Department(102, "D-BB"));
        departments.put(103, new Department(103, "D-CC"));
        departments.put(104, new Department(104, "D-DD"));
        departments.put(105, new Department(105, "D-EE"));
    }
    
    public Collection<Department> getDepartments(){
        return departments.values();
    }
    
    public Department getDepartment(Integer id){
        return departments.get(id);
    }
    
}

准备工作差不多了，接下就是编写CRUD

一、

1、做一个用户名密码校验

@Controller
public class LoginController {
    @PostMapping("/user/login")
//    @RequestMapping(value = "/user/login",method = RequestMethod.POST)
    public String login(@RequestParam("username") String username,@RequestParam("password") String password,
                        Map<String,Object> map,HttpSession session ){
        if(!StringUtils.isEmpty(username)&&"123".equals(password)){
//            登陆成功，防止表单重复提交，可以重定向到主页
            session.setAttribute("loginUser",username);
            return "redirect:/main.html";
        }else{
            map.put("msg","用户名或密码错误");
            return "login";
        }

    }
}

2、做一个非法请求过滤

/**
 * 登录检查
 */
public class LoginHandlerInterceptor implements HandlerInterceptor {

    @Override
//   执行前
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        Object loginUser = request.getSession().getAttribute("loginUser");
        if (loginUser == null) {
//            未登录，返回登录页
            request.setAttribute("msg", "没有权限请先登录");
            request.getRequestDispatcher("/index.html").forward(request, response);
            return false;
        } else {
//            已登录，放行
            return true;
        }

    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {

    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {

    }
}

配置完记得在@Configuration标识的配置类中注册

CRUD代码比较简单，直接贴代码

@Controller
public class EmployeeController {
    @Autowired
    EmployeeDao employeeDao;
    @Autowired
    DepartmentDao departmentDao;

    //    查询所有员工返回列表页面
    @GetMapping("emps")
    public String list(Model model) {
        Collection<Employee> all = employeeDao.getAll();
//        放在请求域中
        model.addAttribute("emps", all);
        return "emp/list";
    }

    //    来到员工添加页面
    @GetMapping("/emp")
    public String toAddPage(Model model) {
//        去添加页面之前，先查出所有部门在页面显示
        Collection<Department> departments = departmentDao.getDepartments();
        model.addAttribute("depts", departments);
        return "emp/add";
    }

    //   员工添加
//    SpringMVC 自动将请求参数和入参对象的属性进行一一绑定：要求了请求参数的名字和JavaBean入参对象里面的属性名是一样的
    @PostMapping("/emp")
    public String AddEmp(Employee employee) {
//        添加完成后来到员工列表页面
        System.out.println("保存的员工信息"+employee);
        employeeDao.save(employee);
//        redirect: 表示重定向到一个地址  / 代表当前项目路径
//        forward：表示转发到一个地址
        return "redirect:/emps";
    }
//    去修改页面,查出信息并回显
    @GetMapping("/emp/{id}")
    public String toEditPaage(@PathVariable("id") Integer id ,Model model){
        Employee employee = employeeDao.get(id);
        model.addAttribute("emp",employee);
//        页面要显示所有的部门列表
        Collection<Department> departments = departmentDao.getDepartments();
        model.addAttribute("depts", departments);
//        回到修改页面(add是一个修改添加二合一的页面)
        return "emp/add";
    }
//    员工修改:需要提交员工id
    @PutMapping("/emp")
    public String updateEmployee(Employee employee){
        System.out.println("修改的数据"+employee);
        employeeDao.save(employee);
        return "redirect:/emps";
    }
//    员工删除
    @DeleteMapping("/emp/{id}")
    public String deleteEmployee(@PathVariable("id") Integer id){
        employeeDao.delete(id);
        return "redirect:/emps";
    }
}