《Pro Spring Boot 2》第四章：Web Applications with Spring Boot

The Spring MVC is designed around the org.springframework.web.servlet. DispatcherServlet class. This servlet is very flexible and has a very robust functionality that you won’t find in any other MVC web framework out there. With the DispatcherServlet, you have several out-of-the-box resolutions strategies, including view resolvers, locale resolvers, theme resolvers, and exception handlers. In other words, the DispatcherServlet take a HTTP request and redirect it to the right handler (the class marked with the @Controller or @RestController and the methods that use the @RequestMapping annotations) and the right view (your JSPs).

package com.apress.todo.domain;

import lombok.Data;

import javax.validation.constraints.NotBlank;
import javax.validation.constraints.NotNull;
import java.time.LocalDateTime;
import java.util.UUID;

@Data
public class ToDo {

    @NotNull
    private String id;
    @NotNull
    @NotBlank
    private String description;
    private LocalDateTime created;
    private LocalDateTime modified;
    private boolean completed;

    public ToDo(){
        LocalDateTime date = LocalDateTime.now();
        this.id = UUID.randomUUID().toString();
        this.created = date;
        this.modified = date;
    }

    public ToDo(String description){
        this();
        this.description = description;
    }
}

shows you the ToDo class, which has all the required fields. It also uses the @Data annotation, which is a Lombok annotation that generates a default constructor (if you don’t have one) and all the setters, getters, and overrides, such as the toString method, to make the class cleaner. Also note that the class has the @NotNull and @NotBlank annotations in some of the fields; these annotations are used in the validation that we do later on. The default constructor has field initialization, so it is easy to create a ToDo instance

package com.apress.todo.repository;

import com.apress.todo.domain.ToDo;
import org.springframework.stereotype.Repository;

import java.time.LocalDateTime;
import java.util.Collection;
import java.util.Comparator;
import java.util.HashMap;
import java.util.Map;
import java.util.stream.Collectors;

@Repository
public class ToDoRepository implements CommonRepository<ToDo> {

    private Map<String,ToDo> toDos = new HashMap<>();

    @Override
    public ToDo save(ToDo domain) {
        ToDo result = toDos.get(domain.getId());
        if(result != null) {
            result.setModified(LocalDateTime.now());
            result.setDescription(domain.getDescription());
            result.setCompleted(domain.isCompleted());
            domain = result;
        }
        toDos.put(domain.getId(), domain);
        return toDos.get(domain.getId());

    }

    @Override
    public Iterable<ToDo> save(Collection<ToDo> domains) {
        domains.forEach(this::save);
        return findAll();
    }

    @Override
    public void delete(ToDo domain) {
        toDos.remove(domain.getId());
    }

    @Override
    public ToDo findById(String id) {
        return toDos.get(id);
    }

    @Override
    public Iterable<ToDo> findAll() {
        return toDos.entrySet().stream().sorted(entryComparator).map(Map.Entry::getValue).collect(Collectors.toList());
    }

    private Comparator<Map.Entry<String,ToDo>> entryComparator = (Map.Entry<String, ToDo> o1, Map.Entry<String, ToDo> o2) -> {
        return o1.getValue().getCreated().compareTo(o2.getValue().getCreated());
    };
}

package com.apress.todo.validation;

import com.fasterxml.jackson.annotation.JsonInclude;

import java.util.ArrayList;
import java.util.List;

public class ToDoValidationError {

    @JsonInclude(JsonInclude.Include.NON_EMPTY)
    private List<String> errors = new ArrayList<>();

    private final String errorMessage;

    public ToDoValidationError(String errorMessage) {
        this.errorMessage = errorMessage;
    }

    public void addValidationError(String error) {
        errors.add(error);
    }

    public List<String> getErrors() {
        return errors;
    }

    public String getErrorMessage() {
        return errorMessage;
    }
}

package com.apress.todo.validation;

import org.springframework.validation.Errors;
import org.springframework.validation.ObjectError;

public class ToDoValidationErrorBuilder {

    public static ToDoValidationError fromBindingErrors(Errors errors) {
        ToDoValidationError error = new ToDoValidationError("Validation failed. " + errors.getErrorCount() + " error(s)");
        for (ObjectError objectError : errors.getAllErrors()) {
            error.addValidationError(objectError.getDefaultMessage());
        }
        return error;
    }
}

package com.apress.todo.controller;

import com.apress.todo.domain.ToDo;
import com.apress.todo.domain.ToDoBuilder;
import com.apress.todo.repository.CommonRepository;
import com.apress.todo.validation.ToDoValidationError;
import com.apress.todo.validation.ToDoValidationErrorBuilder;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.validation.Errors;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.servlet.support.ServletUriComponentsBuilder;

import javax.validation.Valid;
import java.net.URI;

@RestController
@RequestMapping("/api")
public class ToDoController {

    private CommonRepository<ToDo> repository;

    @Autowired
    public ToDoController(CommonRepository<ToDo> repository) {
        this.repository = repository;
    }

    @GetMapping("/todo") //@RequestMapping(value="/todo", method = {RequestMethod.GET})
    public ResponseEntity<Iterable<ToDo>> getToDos(){
        return ResponseEntity.ok(repository.findAll());
    }

    @GetMapping("/todo/{id}")
    public ResponseEntity<ToDo> getToDoById(@PathVariable String id){
        return ResponseEntity.ok(repository.findById(id));
    }

    @PatchMapping("/todo/{id}")
    public ResponseEntity<ToDo> setCompleted(@PathVariable String id){
        ToDo result = repository.findById(id);
        result.setCompleted(true);
        repository.save(result);
        URI location = ServletUriComponentsBuilder.fromCurrentRequest()
                .buildAndExpand(result.getId()).toUri();

        return ResponseEntity.ok().header("Location",location.toString()).build();
    }

    @RequestMapping(value="/todo", method = {RequestMethod.POST,RequestMethod.PUT})
    public ResponseEntity<?> createToDo(@Valid @RequestBody ToDo toDo, Errors errors){
        if (errors.hasErrors()) {
            return ResponseEntity.badRequest().body(ToDoValidationErrorBuilder.fromBindingErrors(errors));
        }

        ToDo result = repository.save(toDo);
        URI location = ServletUriComponentsBuilder.fromCurrentRequest().path("/{id}")
                .buildAndExpand(result.getId()).toUri();
        return ResponseEntity.created(location).build();
    }

    @DeleteMapping("/todo/{id}")
    public ResponseEntity<ToDo> deleteToDo(@PathVariable String id){
        repository.delete(ToDoBuilder.create().withId(id).build());
        return ResponseEntity.noContent().build();
    }

    @DeleteMapping("/todo")
    public ResponseEntity<ToDo> deleteToDo(@RequestBody ToDo toDo){
        repository.delete(toDo);
        return ResponseEntity.noContent().build();
    }

    @ExceptionHandler
    @ResponseStatus(value = HttpStatus.BAD_REQUEST)
    public ToDoValidationError handleException(Exception exception) {
        return new ToDoValidationError(exception.getMessage());
    }

}

原文地址：https://www.cnblogs.com/JasonPeng1/p/12267444.html