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。
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>
接下来我们需要创建一个应用程序的主类:
@SpringBootApplication public 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=8081
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="${appName}">Our App</span></p> </body> </html>
最后创建一个Controller指向这个页面:
@Controller public class SimpleController { @Value("${spring.application.name}") String appName; @GetMapping("/") public String homePage(Model model) { model.addAttribute("appName", appName); return "home"; } }
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 @EnableWebSecurity public class SecurityConfig extends WebSecurityConfigurerAdapter { @Override protected 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。
本例中,我们定义一个Book类,那么需要定义相应的Entity类:
@Entity public 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。
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 { @Autowired private BookRepository bookRepository; @GetMapping public 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。
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:
@ControllerAdvice public 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。
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 { @Test public 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"); } @Test public void whenGetAllBooks_thenOK() { Response response = RestAssured.get(API_ROOT); assertEquals(HttpStatus.OK.value(), response.getStatusCode()); } @Test public 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); } @Test public 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")); } @Test public void whenGetNotExistBookById_thenNotFound() { Response response = RestAssured.get(API_ROOT + "/" + randomNumeric(4)); assertEquals(HttpStatus.NOT_FOUND.value(), response.getStatusCode()); } @Test public 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()); } @Test public 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()); } @Test public 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")); } @Test public 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。
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