《Pro Spring Boot 2》第四章（Web Applications with Spring Boot） _Applications

幽沉谢世事，俯默窥唐虞。这篇文章主要讲述《Pro Spring Boot 2》第四章：Web Applications with Spring Boot相关的知识，希望能为你提供帮助。

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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).

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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

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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()); }; }

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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; } }

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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; } }

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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="https://www.songbingjia.com/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="https://www.songbingjia.com/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 = https://www.songbingjia.com/android/HttpStatus.BAD_REQUEST) public ToDoValidationError handleException(Exception exception) { return new ToDoValidationError(exception.getMessage()); }}

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【《Pro Spring Boot 2》第四章（Web Applications with Spring Boot）】

package com.apress.todo.client.domain; import lombok.Data; import java.time.LocalDateTime; import java.util.UUID; @Data public class ToDo {private String id; 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; } }

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package com.apress.todo.client.error; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.http.client.ClientHttpResponse; import org.springframework.util.StreamUtils; import org.springframework.web.client.DefaultResponseErrorHandler; import java.io.IOException; import java.nio.charset.Charset; public class ToDoErrorHandler extends DefaultResponseErrorHandler {private Logger log = LoggerFactory.getLogger(ToDoErrorHandler.class); @Override public void handleError(ClientHttpResponse response) throws IOException { log.error(response.getStatusCode().toString()); log.error(StreamUtils.copyToString(response.getBody(),Charset.defaultCharset())); }}

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package com.apress.todo.client; import lombok.Data; import org.springframework.boot.context.properties.ConfigurationProperties; import org.springframework.stereotype.Component; @Component @ConfigurationProperties(prefix="todo") @Data public class ToDoRestClientProperties {private String url; private String basePath; }

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package com.apress.todo.client; import com.apress.todo.client.domain.ToDo; import com.apress.todo.client.error.ToDoErrorHandler; import org.springframework.boot.context.properties.EnableConfigurationProperties; import org.springframework.core.ParameterizedTypeReference; import org.springframework.http.*; import org.springframework.stereotype.Service; import org.springframework.web.client.RestTemplate; import java.net.URI; import java.net.URISyntaxException; import java.util.HashMap; import java.util.Map; @Service public class ToDoRestClient {private RestTemplate restTemplate; private ToDoRestClientProperties properties; public ToDoRestClient(ToDoRestClientProperties properties){ this.restTemplate = new RestTemplate(); this.restTemplate.setErrorHandler(new ToDoErrorHandler()); this.properties = properties; }public Iterable< ToDo> findAll() throws URISyntaxException { RequestEntity< Iterable< ToDo> > requestEntity = new RequestEntity< Iterable< ToDo> > (HttpMethod.GET,new URI(properties.getUrl() + properties.getBasePath())); ResponseEntity< Iterable< ToDo> > response = restTemplate.exchange(requestEntity,new ParameterizedTypeReference< Iterable< ToDo> > (){}); if(response.getStatusCode() == HttpStatus.OK){ return response.getBody(); }return null; }public ToDo findById(String id){ Map< String, String> params = new HashMap< String, String> (); params.put("id", id); return restTemplate.getForObject(properties.getUrl() + properties.getBasePath() + "/{id}",ToDo.class,params); }public ToDo upsert(ToDo toDo) throws URISyntaxException { RequestEntity< ?> requestEntity = new RequestEntity< > (toDo,HttpMethod.POST,new URI(properties.getUrl() + properties.getBasePath())); ResponseEntity< ?> response = restTemplate.exchange(requestEntity, new ParameterizedTypeReference< ToDo> () {}); if(response.getStatusCode() == HttpStatus.CREATED){ return restTemplate.getForObject(response.getHeaders().getLocation(),ToDo.class); } return null; }public ToDo setCompleted(String id) throws URISyntaxException{ Map< String, String> params = new HashMap< String, String> (); params.put("id", id); restTemplate.postForObject(properties.getUrl() + properties.getBasePath() + "/{id}?_method=patch",null, ResponseEntity.class, params); return findById(id); }public void delete(String id){ Map< String, String> params = new HashMap< String, String> (); params.put("id", id); restTemplate.delete(properties.getUrl() + properties.getBasePath() + "/{id}",params); }}

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package com.apress.todo; import com.apress.todo.client.ToDoRestClient; import com.apress.todo.client.domain.ToDo; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.boot.CommandLineRunner; import org.springframework.boot.SpringApplication; import org.springframework.boot.WebApplicationType; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.context.annotation.Bean; @SpringBootApplication public class TodoClientApplication {public static void main(String[] args) { SpringApplication app = new SpringApplication(TodoClientApplication.class); app.setWebApplicationType(WebApplicationType.NONE); app.run(args); }private Logger log = LoggerFactory.getLogger(TodoClientApplication.class); @Bean public CommandLineRunner process(ToDoRestClient client){ return args -> {Iterable< ToDo> toDos = client.findAll(); assert toDos != null; toDos.forEach( toDo -> log.info(toDo.toString())); ToDo newToDo = client.upsert(new ToDo("Drink plenty of Water daily!")); assert newToDo != null; log.info(newToDo.toString()); ToDo toDo = client.findById(newToDo.getId()); assert toDos != null; log.info(toDo.toString()); ToDo completed = client.setCompleted(newToDo.getId()); assert completed.isCompleted(); log.info(completed.toString()); client.delete(newToDo.getId()); assert client.findById(newToDo.getId()) == null; }; } }