Spring Boot是Spring平台的约定式的应用框架,使用Spring Boot可以更加方便简洁的开发基于Spring的应用程序,本篇文章通过一个实际的例子,来一步一步的演示如何创建一个基本的Spring Boot程序。
依赖配置本例子使用Maven来做包的依赖管理,在pom.xml文件中我们需要添加Spring boot依赖:
<parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.2.2.RELEASE</version><relativePath/> <!-- lookup parent from repository --></parent>
同时我们要构建一个web应用程序,所以需要添加web依赖:
<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency>
OOM框架,我们使用spring自带的jpa,数据库使用内存数据库H2:
<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-data-jpa</artifactId></dependency><dependency><groupId>com.h2database</groupId><artifactId>h2</artifactId><scope>runtime</scope></dependency>main程序配置
接下来我们需要创建一个应用程序的主类:
@SpringBootApplicationpublic class App {public static void main(String[] args) {SpringApplication.run(App.class, args);}}
这里我们使用了注解: @SpringBootApplication。 它等同于三个注解:@Configuration, @EnableAutoConfiguration, 和 @ComponentScan同时使用。
最后,我们需要在resources目录中添加属性文件:application.properties。 在其中我们定义程序启动的端口:
server.port=8081MVC配置
spring MVC可以配合很多模板语言使用,这里我们使用Thymeleaf。
首先需要添加依赖:
<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-thymeleaf</artifactId> </dependency>
然后在application.properties中添加如下配置:
spring.thymeleaf.cache=false spring.thymeleaf.enabled=true spring.thymeleaf.prefix=classpath:/templates/ spring.thymeleaf.suffix=.html spring.application.name=Bootstrap Spring Boot
然后创建一个home页面:
<html><head><title>Home Page</title></head><body><h1>Hello !</h1><p>Welcome to <span th:text="${appName}">Our App</span></p></body></html>
最后创建一个Controller指向这个页面:
@Controllerpublic class SimpleController {@Value("${spring.application.name}")String appName; @GetMapping("/")public String homePage(Model model) {model.addAttribute("appName", appName);return "home";}}安全配置
本例主要是搭一个基本完整的框架,所以必须的安全访问控制也是需要的。我们使用Spring Security来做安全控制,加入依赖如下:
<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-security</artifactId> </dependency>
当spring-boot-starter-security加入依赖之后,应用程序所有的入库会被默认加入权限控制,在本例中,我们还用不到这些权限控制,所以需要自定义SecurityConfig,放行所有的请求:
@Configuration@EnableWebSecuritypublic class SecurityConfig extends WebSecurityConfigurerAdapter { @Overrideprotected void configure(HttpSecurity http) throws Exception {http.authorizeRequests().anyRequest().permitAll().and().csrf().disable();}}
上例中,我们permit all请求。
后面我又会详细的关于Spring Security的教程。这里先不做深入讨论。
存储本例中,我们定义一个Book类,那么需要定义相应的Entity类:
@Entitypublic class Book { @Id@GeneratedValue(strategy = GenerationType.AUTO)private long id; @Column(nullable = false, unique = true)private String title; @Column(nullable = false)private String author;}
和相应的Repository类:
public interface BookRepository extends CrudRepository<Book, Long> {List<Book> findByTitle(String title);}
最后,我们需要让应用程序发现我们配置的存储类,如下:
@EnableJpaRepositories("com.flydean.learn.repository") @EntityScan("com.flydean.learn.entity") @SpringBootApplication public class App { public static void main(String[] args) { SpringApplication.run(App.class, args); } }
这里,我们使用@EnableJpaRepositories 来扫描repository类。
使用@EntityScan来扫描JPA entity类。
为了方便起见,我们使用内存数据库H2. 一旦H2在依赖包里面,Spring boot会自动检测到,并使用它。 我们需要配置一些H2的属性:
spring.datasource.driver-class-name=org.h2.Driver spring.datasource.url=jdbc:h2:mem:bootapp;DB_CLOSE_DELAY=-1 spring.datasource.username=sa spring.datasource.password=
和安全一样,存储也是一个非常重要和复杂的课题,我们也会在后面的文章中讨论。
Web 页面和Controller有了Book entity, 我们需要为Book写一个Controller,主要做增删改查的操作,如下所示:
@RestController@RequestMapping("/api/books")public class BookController {@Autowiredprivate BookRepository bookRepository;@GetMappingpublic Iterable findAll() {return bookRepository.findAll();}@GetMapping("/title/{bookTitle}")public List findByTitle(@PathVariable String bookTitle) {return bookRepository.findByTitle(bookTitle);}@GetMapping("/{id}")public Book findOne(@PathVariable Long id) {return bookRepository.findById(id).orElseThrow(BookNotFoundException::new);}@PostMapping@ResponseStatus(HttpStatus.CREATED)public Book create(@RequestBody Book book) {return bookRepository.save(book);}@DeleteMapping("/{id}")public void delete(@PathVariable Long id) {bookRepository.findById(id).orElseThrow(BookNotFoundException::new);bookRepository.deleteById(id);}@PutMapping("/{id}")public Book updateBook(@RequestBody Book book, @PathVariable Long id) {if (book.getId() != id) {throw new BookIdMismatchException("ID mismatch!");}bookRepository.findById(id).orElseThrow(BookNotFoundException::new);return bookRepository.save(book);}}
这里我们使用@RestController 注解,表示这个Controller是一个API,不涉及到页面的跳转。
@RestController是@Controller 和 @ResponseBody 的集合。
异常处理基本上我们的程序已经完成了,但是在Controller中,我们定义了一些自定义的异常:
public class BookNotFoundException extends RuntimeException { public BookNotFoundException(String message, Throwable cause) {super(message, cause);}// ...}
那么怎么处理这些异常呢?我们可以使用@ControllerAdvice来拦截这些异常:
@ControllerAdvicepublic class RestExceptionHandler extends ResponseEntityExceptionHandler { @ExceptionHandler({ BookNotFoundException.class })protected ResponseEntity<Object> handleNotFound( Exception ex, WebRequest request) {return handleExceptionInternal(ex, "Book not found", new HttpHeaders(), HttpStatus.NOT_FOUND, request);} @ExceptionHandler({ BookIdMismatchException.class, ConstraintViolationException.class, DataIntegrityViolationException.class })public ResponseEntity<Object> handleBadRequest( Exception ex, WebRequest request) {return handleExceptionInternal(ex, ex.getLocalizedMessage(), new HttpHeaders(), HttpStatus.BAD_REQUEST, request);}}
这种异常捕获也叫做全局异常捕获。
测试我们的Book API已经写好了,接下来我们需要写一个测试程序来测试一下。
这里我们使用@SpringBootTest :
@Slf4j@RunWith(SpringRunner.class)@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.DEFINED_PORT)public class SpringContextTest {@Testpublic void contextLoads() {log.info("contextLoads");}}
webEnvironment = SpringBootTest.WebEnvironment.DEFINED_PORT的作用是表示测试时候使用的Spring boot应用程序端口使用自定义在application.properties中的端口。
接下来我们使用RestAssured来测试BookController:
@RunWith(SpringRunner.class)@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.DEFINED_PORT)public class SpringBootBootstrapTest {private static final String API_ROOT= "http://localhost:8081/api/books";private Book createRandomBook() {Book book = new Book();book.setTitle(randomAlphabetic(10));book.setAuthor(randomAlphabetic(15));return book;}private String createBookAsUri(Book book) {Response response = RestAssured.given().contentType(MediaType.APPLICATION_JSON_VALUE).body(book).post(API_ROOT);return API_ROOT + "/" + response.jsonPath().get("id");}@Testpublic void whenGetAllBooks_thenOK() {Response response = RestAssured.get(API_ROOT);assertEquals(HttpStatus.OK.value(), response.getStatusCode());}@Testpublic void whenGetBooksByTitle_thenOK() {Book book = createRandomBook();createBookAsUri(book);Response response = RestAssured.get(API_ROOT + "/title/" + book.getTitle());assertEquals(HttpStatus.OK.value(), response.getStatusCode());assertTrue(response.as(List.class).size() > 0);}@Testpublic void whenGetCreatedBookById_thenOK() {Book book = createRandomBook();String location = createBookAsUri(book);Response response = RestAssured.get(location);assertEquals(HttpStatus.OK.value(), response.getStatusCode());assertEquals(book.getTitle(), response.jsonPath().get("title"));}@Testpublic void whenGetNotExistBookById_thenNotFound() {Response response = RestAssured.get(API_ROOT + "/" + randomNumeric(4));assertEquals(HttpStatus.NOT_FOUND.value(), response.getStatusCode());}@Testpublic void whenCreateNewBook_thenCreated() {Book book = createRandomBook();Response response = RestAssured.given().contentType(MediaType.APPLICATION_JSON_VALUE).body(book).post(API_ROOT);assertEquals(HttpStatus.CREATED.value(), response.getStatusCode());}@Testpublic void whenInvalidBook_thenError() {Book book = createRandomBook();book.setAuthor(null);Response response = RestAssured.given().contentType(MediaType.APPLICATION_JSON_VALUE).body(book).post(API_ROOT);assertEquals(HttpStatus.BAD_REQUEST.value(), response.getStatusCode());}@Testpublic void whenUpdateCreatedBook_thenUpdated() {Book book = createRandomBook();String location = createBookAsUri(book);book.setId(Long.parseLong(location.split("api/books/")[1]));book.setAuthor("newAuthor");Response response = RestAssured.given().contentType(MediaType.APPLICATION_JSON_VALUE).body(book).put(location);assertEquals(HttpStatus.OK.value(), response.getStatusCode());response = RestAssured.get(location);assertEquals(HttpStatus.OK.value(), response.getStatusCode());assertEquals("newAuthor", response.jsonPath().get("author"));}@Testpublic void whenDeleteCreatedBook_thenOk() {Book book = createRandomBook();String location = createBookAsUri(book);Response response = RestAssured.delete(location);assertEquals(HttpStatus.OK.value(), response.getStatusCode());response = RestAssured.get(location);assertEquals(HttpStatus.NOT_FOUND.value(), response.getStatusCode());}}
写好了测试类,运行就行了。
结论你的第一个Spring Boot程序就完成了,后面的文章我们会继续丰富和改善这个基本框架,欢迎继续关注。
本文章的例子代码可以参考github: bootstrap-sample-app