在程序員的平常工做中,Web開發應該是佔比很重的一部分,至少我工做以來,開發的系統基本都是Web端訪問的系統,Web開發在這幾年也是經歷了很快的發展,前端也顯得愈來愈重要,如今不少大一點的公司都實行先後端分離,讓後端和前端只專一於本身的事,所謂術業有專攻,我我的也很是建議先後端分離。html
既然先後端分離了,那麼後端確定須要提供Web Api接口給到前端,並返回前端須要的數據。前端
在Spring Boot中,開發Web Api接口主要使用如下幾個註解:java
其實,這些註解在Spring MVC裏都有了,因此Spring Boot裏的用法也和Spring MVC裏基本同樣。git
在Spring Boot之因此能使用,是由於在spring-boot-starter-web 這個starter pom中,已經引用了spring-web和spring-webmvc。程序員
接下來,咱們經過具體例子來說解下各個註解的使用方法。github
新建控制器HelloController,添加@Controller註解,添加1個方法sayHello,添加@RequestMapping註解,代碼以下:web
package com.zwwhnly.springbootdemo.controller;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
@Controller
public class HelloController {
@RequestMapping(value = "/hello", method = RequestMethod.GET)
public String sayHello() {
return "hello";
}
}
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運行項目,在瀏覽器輸入http://localhost:8080/hello訪問,發現報以下錯誤:spring
報錯的緣由是未找到對應的模板,那麼如何解決呢?json
咱們先講解下第一種解決方法,添加下thymeleaf模板,首先修改pom文件,添加以下配置:後端
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>
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若是沒有設置自動導入maven包的話,IDEA右下角會提示你導入,點擊「Import Changes」。
而後在resources/templates目錄下,新建hello.html文件(內容先隨便寫),再次運行項目,訪問http://localhost:8080/hello,發現訪問正常:
還有一種更簡單的方法是在控制器上添加@ResponseBody註解:
package com.zwwhnly.springbootdemo.controller;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;
@Controller
@ResponseBody
public class HelloController {
@RequestMapping(value = "/hello", method = RequestMethod.GET)
public String sayHello() {
return "hello";
}
}
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此時的運行結果(直接返回字符串):
hello
@RestController是Spring4.0推出的組合註解,至關於@Controller+@ResponseBody,咱們看下它的源碼,也能看出:
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Controller
@ResponseBody
public @interface RestController {
@AliasFor(
annotation = Controller.class
)
String value() default "";
}
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此時咱們就能夠將代碼簡化爲:
@RestController
public class HelloController {
@RequestMapping(value = "/hello", method = RequestMethod.GET)
public String sayHello() {
return "hello";
}
}
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@RequestMapping註解主要用來配置url映射,既能夠添加到控制器上,也能夠添加到控制器下的方法上,添加到方法上是對添加到控制器上的補充,舉例說明:
新建圖書類Book:
package com.zwwhnly.springbootdemo.model;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
public class Book {
private Integer bookId;
private String bookName;
private String bookAuthor;
private Date purchaseDate;
public Book(Integer bookId, String bookName, String bookAuthor, String purchaseDate) throws ParseException {
SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
this.bookId = bookId;
this.bookName = bookName;
this.bookAuthor = bookAuthor;
this.purchaseDate = simpleDateFormat.parse(purchaseDate);
}
public Integer getBookId() {
return bookId;
}
public void setBookId(Integer bookId) {
this.bookId = bookId;
}
public String getBookName() {
return bookName;
}
public void setBookName(String bookName) {
this.bookName = bookName;
}
public String getBookAuthor() {
return bookAuthor;
}
public void setBookAuthor(String bookAuthor) {
this.bookAuthor = bookAuthor;
}
public Date getPurchaseDate() {
return purchaseDate;
}
public void setPurchaseDate(Date purchaseDate) {
this.purchaseDate = purchaseDate;
}
}
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在HelloController中添加方法getBookList:
@RequestMapping(value = "/getBookList", method = RequestMethod.GET)
public List<Book> getBookList() {
List<Book> books = new ArrayList<>();
try {
Book book1 = new Book(1, "平凡的世界", "路遙", "2010-01-01");
Book book2 = new Book(2, "人生", "路遙", "2011-01-01");
books.add(book1);
books.add(book2);
} catch (ParseException e) {
e.printStackTrace();
}
return books;
}
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運行項目在瀏覽器輸入http://localhost:8080/getBookList,結果爲:
// 20190424140621
// http://localhost:8080/getBookList
[
{
"bookId": 1,
"bookName": "平凡的世界",
"bookAuthor": "路遙",
"purchaseDate": "2009-12-31 16:00:00"
},
{
"bookId": 2,
"bookName": "人生",
"bookAuthor": "路遙",
"purchaseDate": "2010-12-31 16:00:00"
}
]
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而後咱們在HelloController上也加上@RequestMapping註解:
package com.zwwhnly.springbootdemo.controller;
import com.zwwhnly.springbootdemo.model.Book;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
import java.text.ParseException;
import java.util.ArrayList;
import java.util.List;
@RestController
@RequestMapping(value = "hello")
public class HelloController {
@RequestMapping(value = "/hello", method = RequestMethod.GET)
public String sayHello() {
return "hello";
}
@RequestMapping(value = "/getBookList", method = RequestMethod.GET)
public List<Book> getBookList() {
List<Book> books = new ArrayList<>();
try {
Book book1 = new Book(1, "平凡的世界", "路遙", "2010-01-01");
Book book2 = new Book(2, "人生", "路遙", "2011-01-01");
books.add(book1);
books.add(book2);
} catch (ParseException e) {
e.printStackTrace();
}
return books;
}
}
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此時兩個方法的訪問地址就分別變爲了:http://localhost:8080/hello/hello,http://localhost:8080/hello/getBookList。
@PathVariable註解用來獲取url中的數據,如下爲具體的使用方法,
在HelloController控制器中添加方法getBook,經過佔位符傳遞bookId:
@RequestMapping(value = "/getBook/{bookId}", method = RequestMethod.GET)
public Book getBook(@PathVariable Integer bookId) {
Book book = null;
List<Book> books = new ArrayList<>();
try {
Book book1 = new Book(1, "平凡的世界", "路遙", "2010-01-01");
Book book2 = new Book(2, "人生", "路遙", "2011-01-01");
books.add(book1);
books.add(book2);
book = books.get(bookId - 1);
} catch (ParseException e) {
e.printStackTrace();
}
return book;
}
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運行項目,在瀏覽器中訪問http://localhost:8080/hello/getBook/1,結果以下:
// 20190424145348
// http://localhost:8080/hello/getBook/1
{
"bookId": 1,
"bookName": "平凡的世界",
"bookAuthor": "路遙",
"purchaseDate": "2009-12-31 16:00:00"
}
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注意:佔位符裏的名稱必須和參數名徹底一致,區分大小寫,不然訪問會報500錯誤。
若是想不一致,能夠寫成以下方式:
@RequestMapping(value = "/getBook/{bookId}", method = RequestMethod.GET)
public Book getBook(@PathVariable("bookId") Integer bookIndex) {
......
}
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這種方式也要求,PathVariable的value屬性值必須與佔位符裏的名稱徹底一致。
好了,本篇文章就先講解這麼多,其它註解後續再單獨發佈文章講解。
原文地址:Spring Boot入門(四):開發Web Api接口經常使用註解總結
博客地址:www.zwwhnly.com
歡迎你們下載,有問題能夠多多交流。
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