前言
java語言在多數時,會作為一個後端語言,為前端的html,node.js等提供API接口。前端通過ajax請求去調用java的API服務。今天以node.js為例,介紹兩種跨域方式:CrossOrigin和反向代理。
一、準備工作
pom.xml:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.example</groupId>
<artifactId>spring-boot-15</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>spring-boot-15</name>
<description>Demo project for Spring Boot</description>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.3.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
pom.xml
App.java
package com.example;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication
@SpringBootApplication
public class App {
public static void main(String[] args) {
SpringApplication.run(App.class, args);
}
}
User.java
package com.example;
public class User {
public int id;
public String name;
public int age;
}
MainController.java:
package com.example;
import java.util.ArrayList;
import java.util.List;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
/**
* 控制器 部落格出處:http://www.cnblogs.com/GoodHelper/
*
*/
@RestController
public class MainController {
@GetMapping("findAllUser")
public List<User> findAllUser() {
List<User> list = new ArrayList<>();
for (int i = 0; i < 20; i++) {
User user = new User();
list.add(user);
user.id = i;
user.name = "name_" + i;
user.age = 20 + i;
}
return list;
}
}
項目結構如下圖所示:
通路http://localhost:8080/findAllUser
使用HBuilder建立node.js express項目:
選擇ejs模闆引擎:
index.ejs檔案代碼如下:
<!DOCTYPE html>
<html>
<head>
<title>
<%= title %>
</title>
<link rel='stylesheet' href='/stylesheets/style.css' />
<script src="//cdn.bootcss.com/angular.js/1.5.6/angular.min.js"></script>
<script type="text/javascript">
var app = angular.module('app', []);
app.controller('MainController', function($rootScope, $scope, $http) {
$http({
method: 'GET',
url: 'http://localhost:8080/findAllUser'
}).then(function successCallback(r) {
$scope.rows = r.data;
});
});
</script>
</head>
<body ng-app="app" ng-controller="MainController">
<h1><%= title %></h1>
<p>Welcome to
<%= title %>
</p>
<br />
<table>
<tr ng-repeat="row in rows">
<td>{{row.id}}</td>
<td>{{row.name}}</td>
<td>{{row.age}}</td>
</tr>
</table>
</body>
</html>
通過angular.js的http方法調用api請求
右鍵運作項目:
運作效果:
發現調用ajax請求時跨域失敗。
二、spring boot背景設定允許跨域
這時,修改MainController類,在方法前加@CrossOrigin注解:
/**
* 控制器 部落格出處:http://www.cnblogs.com/GoodHelper/
*
*/
@RestController
public class MainController {
@CrossOrigin(origins = "http://localhost:3000")
@GetMapping("findAllUser")
public List<User> findAllUser() {
List<User> list = new ArrayList<>();
for (int i = 0; i < 20; i++) {
User user = new User();
list.add(user);
user.id = i;
user.name = "name_" + i;
user.age = 20 + i;
}
return list;
}
}
這是聲明findAllUser方法允許跨域,
也可以修改App.java,來實作全局跨域:
package com.example;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.web.servlet.config.annotation.CorsRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
@SpringBootApplication
public class App {
public static void main(String[] args) {
SpringApplication.run(App.class, args);
}
@Bean
public WebMvcConfigurer corsConfigurer() {
return new WebMvcConfigurerAdapter() {
@Override
public void addCorsMappings(CorsRegistry registry) {
registry.addMapping("/**").allowedOrigins("http://localhost:3000");
}
};
}
}
registry.addMapping("/**"):為根目錄的全部請求,也可以設定為"/user/**",這意味着是user目錄下的所有請求。
在通路http://localhost:3000,效果如下:
三、通過node.js的反向代理實作跨域
node.js提供了一些反向代理的中間件,能輕而易舉的實作跨域,而不需要spring boot做任何設定。
安裝express-http-proxy中間件
npm install --save-dev express-http-proxy
修改app.js檔案,使其支援反向代理:
var proxy = require('express-http-proxy');
var apiProxy = proxy('http://localhost:8080', {});
app.use('/api', apiProxy);
以“/api”開頭的請求轉發為spring boot的API服務。
完整代碼如下:
/**
* Module dependencies.
*/
var express = require('express')
, routes = require('./routes')
, user = require('./routes/user')
, http = require('http')
, path = require('path');
var app = express();
// all environments
app.set('port', process.env.PORT || 3000);
app.set('views', __dirname + '/views');
app.set('view engine', 'ejs');
app.use(express.favicon());
app.use(express.logger('dev'));
app.use(express.bodyParser());
app.use(express.methodOverride());
app.use(app.router);
app.use(express.static(path.join(__dirname, 'public')));
// development only
if ('development' == app.get('env')) {
app.use(express.errorHandler());
}
var proxy = require('express-http-proxy');
var apiProxy = proxy('http://localhost:8080', {});
app.use('/api', apiProxy);
app.get('/', routes.index);
app.get('/users', user.list);
http.createServer(app).listen(app.get('port'), function(){
console.log('Express server listening on port ' + app.get('port'));
});
app.js
修改index.ejs檔案:
var app = angular.module('app', []);
app.controller('MainController', function($rootScope, $scope, $http) {
$http({
method: 'GET',
url: '/api/findAllUser'
}).then(function successCallback(r) {
$scope.rows = r.data;
});
});
完整的index.ejs檔案如下:
<!DOCTYPE html>
<html>
<head>
<title>
<%= title %>
</title>
<link rel='stylesheet' href='/stylesheets/style.css' />
<script src="//cdn.bootcss.com/angular.js/1.5.6/angular.min.js"></script>
<script type="text/javascript">
var app = angular.module('app', []);
app.controller('MainController', function($rootScope, $scope, $http) {
$http({
method: 'GET',
url: '/api/findAllUser'
}).then(function successCallback(r) {
$scope.rows = r.data;
});
});
</script>
</head>
<body ng-app="app" ng-controller="MainController">
<h1><%= title %></h1>
<p>Welcome to
<%= title %>
</p>
<br />
<table>
<tr ng-repeat="row in rows">
<td>{{row.id}}</td>
<td>{{row.name}}</td>
<td>{{row.age}}</td>
</tr>
</table>
</body>
</html>
index.ejs
運作效果如下:
總結
第二種通過反向代理的方式是最佳方案。在正式項目中,可以使用node.js控制web前端渲染與spring boot後端提供API服務的組合。這樣,可以控制使用者在node.js端登入後才能調用spring boot的API服務。在大型web項目中也可以使用node.js的反向代理,把很多子站點關聯起來,這樣便發揮出了網站靈活的擴充性。除了使用node.js的中間件實作跨越以外,同樣能借助nginx等http反向代理伺服器實作跨越。
參考:
https://spring.io/guides/gs/rest-service-cors/
https://www.npmjs.com/package/express-http-proxy
代碼位址:https://github.com/carter659/spring-boot-15.git
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傳回玩轉spring boot系列目錄
作者:劉冬.NET
部落格位址:http://www.cnblogs.com/GoodHelper/
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