Detailed introduction to ajax cross-domain

AJAX cross-domain

Note: Part of the content of this article comes from MOOC.com. @MOOC.com: https://www.imooc.com

Course Introduction

●What is AJAX cross-domain problem

●The reasons for AJAX cross-domain problem

　●Thinking and methods of solving AJAX cross-domain problems

What is AJAX cross-domain problem

●Simply put, when the front end calls the back-end service interface

　●If the service interface is not in the same domain, cross-domain problems will occur

AJAX cross-domain scenario

　●The front-end and back-end separation, service-oriented development model

　● The front-end and back-end development are independent, and the front-end needs to call a large number of back-end interfaces

●As long as the back-end interfaces are not in the same domain, cross-domain problems will occur

●Cross-domain problems are very common and need to be solved Cross-domain issues are also very important

AJAX cross-domain reasons

●Browser restrictions: Browser security verification restrictions

●Cross-domain (protocol, domain name, port any one Different will be considered as cross-domain)

●XHR (XMLHttpRequest) request

AJAX cross-domain problem solving ideas

●Browser: The browser removes cross-domain verification , of little actual value

●XHR: Do not use XHR, use JSONP, which has many disadvantages and cannot meet current development requirements

●Cross-domain: The callee modification supports cross-domain calls ( Specify parameters); the caller modifies the hidden cross-domain (based on proxy)

Write test code

●Called party back-end code writing: Spring Boot

●Caller front-end Code writing: Jquery

●Introducing the front-end Jasmine testing framework

Why do cross-domain problems occur?

The above picture is also very clear, because the browser itself has restrictions for security (same origin).

　●When we send an XMLHttpRequest request, if the requested domain (host domain name, port) is different, then a cross-domain problem will occur (the client cannot obtain the data returned by the server)

It is worth noting that cross-domain problems occur in XMLHttpRequest requests, that is to say, there will be no cross-domain problems if it is not an XMLHttpRequest request

　●A very simple example: When writing a web page, , if the URL is not in this domain, the image can still be obtained normally.

Ideas for solving cross-domain problems

Environment setup

2-1 Back-end project

Code writing

1. Create a maven project pom named ajax-server as follows

<?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.myimooc</groupId>
    <artifactId>ajax-server</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>
    <name>ajax-server</name>
    <description>Demo project for Spring Boot</description>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.1.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-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>

2. Write the AjaxServerStart class

package com.myimooc.ajax.server;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
/**
 * <br>
 * 标题: 启动类<br>
 * 描述: AJAX跨域讲解后端项目<br>
 *
 * @author zc
 * @date 2018/04/18
 */
@SpringBootApplication
public class AjaxServerStart {
    public static void main(String[] args) {
        SpringApplication.run(AjaxServerStart.class, args);
    }
}

3. Write a ResultBean Class

package com.myimooc.ajax.server.vo;
import java.io.Serializable;
/**
 * <br>
 * 标题: REST请求响应POJO类<br>
 * 描述: 封装请求响应结果<br>
 *
 * @author zc
 * @date 2018/04/18
 */
public class ResultBean implements Serializable{
    private static final long serialVersionUID = 7867107433319736719L;
    private String data;
    public ResultBean(String data) {
        this.data = data;
    }
    public String getData() {
        return data;
    }
    public void setData(String data) {
        this.data = data;
    }
}

4. Write TestController class

package com.myimooc.ajax.server.controller;
import com.myimooc.ajax.server.vo.ResultBean;
import com.myimooc.ajax.server.vo.User;
import org.springframework.web.bind.annotation.*;
/**
 * <br>
 * 标题: 测试控制器<br>
 * 描述: 提供REST服务<br>
 * 使用 @CrossOrigin 注解支持跨域，可以放到类或方法上面
 * @author zc
 * @date 2018/04/18
 */
@RestController
@RequestMapping("/test")
//@CrossOrigin
public class TestController {
    @GetMapping("/get1")
    public ResultBean get1() {
        System.out.println("TestController.get1");
        return new ResultBean("get1ok");
    }
    @PostMapping("/postJson")
    public ResultBean postJson(@RequestBody User user) {
        System.out.println("TestController.postJson");
        return new ResultBean("postJson" + user.getName());
    }
    @GetMapping("/getCookie")
    public ResultBean getCookie(@CookieValue(value = "cookie1") String cookie1) {
        System.out.println("TestController.getCookie");
        return new ResultBean("getCookie" + cookie1);
    }
    @GetMapping("/getHeader")
    public ResultBean getHeader(
            @RequestHeader("x-header1") String header1,
            @RequestHeader("x-header2") String header2) {
        System.out.println("TestController.getHeader");
        return new ResultBean("getHeader" + header1+header2);
    }
}

2-2 Front-end project

Code writing

1. Create a maven project pom named ajax-client as follows

<?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.myimooc</groupId>
    <artifactId>ajax-client</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>
    <name>ajax-client</name>
    <description>Demo project for Spring Boot</description>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.1.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.webjars</groupId>
            <artifactId>jquery</artifactId>
            <version>3.3.0</version>
        </dependency>
        <dependency>
            <groupId>org.webjars</groupId>
            <artifactId>jasmine</artifactId>
            <version>2.5.0</version>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

2. Write index.html

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Index</title>
    <link rel="stylesheet" type="text/css" href="/webjars/jasmine/2.5.0/jasmine.css">
    <script src="/webjars/jquery/3.3.0/jquery.min.js"></script>
    <script src="/webjars/jasmine/2.5.0/jasmine.js"></script>
    <script src="/webjars/jasmine/2.5.0/jasmine-html.js"></script>
    <script src="/webjars/jasmine/2.5.0/boot.js"></script>
</head>
<body>
<a href="#" onclick="get1()">发生get1请求</a>
<script>
    function get1() {
        $.getJSON("http://localhost:8080/test/get1").then(
            function (res) {
                console.log(res);
            }
        )
    }
    // 每一个测试用例的超时时间
    jasmine.DEFAULT_TIMEOUT_INTERVAL = 1000;
    // 请求的接口地址前缀
    var base = "http://localhost:8080/test";
    // 测试模块
    describe("AJAX讲解", function () {
        // 测试方法
        it("get1请求", function (done) {
            // 服务器返回的结果
            var result;
            $.getJSON(base + "/get1").then(
                function (res) {
                    result = res;
                }
            );
            // 由于是异步请求，需要使用setTimeout来校验
            setTimeout(function () {
                expect(result).toEqual({
                    "data":"get1ok"
                });
                // 校验完成，通知jasmine框架
                done();
            },100);
        });
        // // 测试方法
        // it("jsonp请求", function (done) {
        //     // 服务器返回的结果
        //     var result;
        //     $.ajax({
        //         url: base + "/get1",
        //         dataType: "jsonp",
        //         jsonp:"callback2",
        //         success: function (res) {
        //             result = res;
        //         }
        //     });
        //
        //     // 由于是异步请求，需要使用setTimeout来校验
        //     setTimeout(function () {
        //         expect(result).toEqual({
        //             "data":"get1ok"
        //         });
        //
        //         // 校验完成，通知jasmine框架
        //         done();
        //     },100);
        // });
        // 测试方法
        it("postJson请求", function (done) {
            // 服务器返回的结果
            var result;
            $.ajax({
                url:base+"/postJson",
                type:"POST",
                contentType:"application/json;charset=utf-8",
                data:JSON.stringify({name:"testName"}),
                success:function(res){
                    result = res;
                }
            });
            // 由于是异步请求，需要使用setTimeout来校验
            setTimeout(function () {
                expect(result).toEqual({
                    "data":"postJsontestName"
                });
                // 校验完成，通知jasmine框架
                done();
            },100);
        });
        it("getCookie请求", function (done) {
            // 服务器返回的结果
            var result;
            $.ajax({
                url:base+"/getCookie",
                xhrFields:{
                    // 发送 AJAX 请求时带上 cookie
                    withCredentials:true
                },
                success:function(res){
                    result = res;
                }
            });
            // 由于是异步请求，需要使用setTimeout来校验
            setTimeout(function () {
                expect(result).toEqual({
                    "data":"getCookietestName"
                });
                // 校验完成，通知jasmine框架
                done();
            },100);
        });
        it("getHeader请求", function (done) {
            // 服务器返回的结果
            var result;
            $.ajax({
                url:base+"/getHeader",
                headers:{
                    "x-header1":"AAA"
                },
                beforeSend:function(xhr){
                   xhr.setRequestHeader("x-header2","BBB")
                },
                success:function(res){
                    result = res;
                }
            });
            // 由于是异步请求，需要使用setTimeout来校验
            setTimeout(function () {
                expect(result).toEqual({
                    "data":"getHeaderAAABBB"
                });
                // 校验完成，通知jasmine框架
                done();
            },100);
        });
    });
</script>
</body>
</html>

3. Write application .properties

server.port=8081

4. Write the AjaxClientStart class

package com.myimooc.ajax.client;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class AjaxClientStart {
    public static void main(String[] args) {
        SpringApplication.run(AjaxClientStart.class, args);
    }
}

5. Start AjaxServerStart and AjaxClientStart, and access http://localhost :8081, click to generate get1 request, resulting in cross-domain problems as follows

Solution to cross-domain

3-1 Prohibition of checking

Cross-domain settings of Chrome browser

●Windows method

Reference document: https://www.cnblogs.com/laden...

Instructions for use: Target input in the properties page Add in the box: --disable-web-security --user-data-dir=C:MyChromeDevUserData

●Mac OS method

Reference document: http://blog.csdn.net/justinji...

　　使用说明：用命令行打开 Google Chrome：open -a "Google Chrome" --args --disable-web-security

3-2 使用JSONP

代码编写

1.编写JsonpAdvice类

package com.myimooc.ajax.server.controller;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.servlet.mvc.method.annotation.AbstractJsonpResponseBodyAdvice;
/**
 * <br>
 * 标题: JSONP 全局处理<br>
 * 描述: 统一处理JSONP<br>
 *
 * @author zc
 * @date 2018/04/18
 */
@ControllerAdvice
public class JsonpAdvice extends AbstractJsonpResponseBodyAdvice{
    public JsonpAdvice() {
        // 与前端约定好回调方法名称，默认是callback
        super("callback2");
    }
}

2.修改index.html

// 测试方法
        it("jsonp请求", function (done) {
            // 服务器返回的结果
            var result;
            $.ajax({
                url: base + "/get1",
                dataType: "jsonp",
                jsonp:"callback2",
                success: function (res) {
                    result = res;
                }
            });
            // 由于是异步请求，需要使用setTimeout来校验
            setTimeout(function () {
                expect(result).toEqual({
                    "data":"get1ok"
                });

                // 校验完成，通知jasmine框架
                done();
            },100);
        });

JSONP的弊端

服务器需要改动代码支持只支持GET发送的不是XHR请求

3-3 支持跨域

常见的JavaEE架构

跨域解决方向

　　●被调用方解决

　　●基于支持跨域的解决思路

　　●基于Http协议关于跨域的相关规定，在响应头里增加指定的字段告诉浏览器，允许调用

　　●跨域请求是直接从浏览器发送到被调用方

　　●修改被调用方的Http服务器

调用方解决

　　●基于隐藏跨域的解决思路

　　●跨域请求不会浏览器直接发送到被调用方

　　●而是从中间的Http服务器（Apache、Nginx）转发过去

　　●修改调用方的Http服务器

被调用方支持跨域

　　●【重点】Web应用服务器（Tomcat、Netty、WebLogic或应用程序）实现

　　●Http服务器（Nginx）配置实现

　　●Http服务器（Apache）配置实现

使用Filter解决

编写代码

1.编写CrosFilter类

package com.myimooc.ajax.server.config;
import org.springframework.util.StringUtils;
import javax.servlet.*;
import javax.servlet.FilterConfig;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
/**
 * <br>
 * 标题: 服务端解决跨域<br>
 * 描述: 使用Filter<br>
 *
 * @author zc
 * @date 2018/04/18
 */
public class CrosFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    }
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        HttpServletResponse res = (HttpServletResponse)response;
        HttpServletRequest req = (HttpServletRequest)request;
        // 支持所有域
        String origin = req.getHeader("Origin");
        if (!StringUtils.isEmpty(origin)){
            // 支持任何域名的跨域调用 且 支持带cookie（是被调用方域名的cookie，而不是调用方的cookie）
            res.addHeader("Access-Control-Allow-Origin",origin);
        }
        // 指定允许的域，带cookie时，origin必须是全匹配，不能使用 *
//        res.addHeader("Access-Control-Allow-Origin","http://localhost:8081");
        // 允许所有域，但不能满足带 cookie 的跨域请求
//        res.addHeader("Access-Control-Allow-Origin","*");
        // 支持所有自定义头
        String headers = req.getHeader("Access-Control-Allow-Headers");
        if (!StringUtils.isEmpty(headers)){
            // 允许所有header
            res.addHeader("Access-Control-Allow-Headers",headers);
        }
        // 允许所有header
//        res.addHeader("Access-Control-Allow-Headers","*");
        // 指定允许的方法
//        res.addHeader("Access-Control-Allow-Methods","GET");
        // 允许所有方法
        res.addHeader("Access-Control-Allow-Methods","*");
        // 允许浏览器在一个小时内，缓存跨域访问信息（即上面三个信息）
        res.addHeader("Access-Control-Max-Age","3600");
        // 启用 cookie
        res.addHeader("Access-Control-Allow-Credentials","true");
        chain.doFilter(request,response);
    }
    @Override
    public void destroy() {
    }
}

2.编写FilterConfig类

package com.myimooc.ajax.server.config;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
/**
 * <br>
 * 标题: 配置类<br>
 * 描述: 注册CrosFilter<br>
 *
 * @author zc
 * @date 2018/04/18
 */
@Configuration
public class FilterConfig {
    @Bean
    public FilterRegistrationBean registrationBean(){
        FilterRegistrationBean filter = new FilterRegistrationBean();
        filter.addUrlPatterns("/*");
        filter.setFilter(new CrosFilter());
        return filter;
    }
}

3.启动AjaxServerStart和AjaxClientStart，并访问http://localhost:8081，跨域解决

简单请求与非简单请求

　　●简单请求：浏览器先发送真正的请求后检查

　　●请求方法：GET、HEAD、POST的一种

　　●请求header：无自定义header；Content-Type为：text/plain、multipart/form-data、application/x-www-form-urlencoded的一种

　　●非简单请求：浏览器先发预检命令，检查通过后，才发送真正的请求

　　●常见的有：PUT、DELETE

　　●其它条件：发送Json格式的请求、带自定义header的请求

　　●预检命令：浏览器检测到跨域请求, 会自动发出一个OPTIONS请求, 就是所谓的预检（preflight）请求。当预检请求通过的时候，才发送真正的请求。

Nginx配置

　　●修改主机hosts文件增加映射本地域名：127.0.0.1 b.com（表示被调用方的域名）

　　●在conf目录下创建vhost目录

　　●修改nginx.conf在最后面增加一行代码：include vhost/*.conf;

　　●在vhost目录下创建b.com.conf

　　●启动niginx，访问b.com/test/get1

编写b.com.conf

server{
    listen 80;
    server_name b.com;
    location /{
        proxy_pass http://localhost:8080/;
        add_header Access-Control-Allow-Methods *;
        add_header Access-Control-Max-Age 3600;
        add_header Access-Control-Allow-Credentials true;
        add_header Access-Control-Allow-Origin $http_origin;
        add_header Access-Control-Allow-Headers $http_access_control_allow_headers;
        if ($request_method = OPTIONS){
            return 200;
        }
    }
}

Apache配置

　　●修改conf/httpd.conf找到LoadModule vhost_alias_module module/mod_vhost_alias.so取消注释

　　●修改conf/httpd.conf找到LoadModule proxy_module module/mod_ proxy.so取消注释

　　●修改conf/httpd.conf找到LoadModule proxy_http_module module/mod_ proxy_http.so取消注释

　　●修改conf/httpd.conf找到LoadModule headers_module module/mod_ headers.so取消注释

　　●修改conf/httpd.conf找到LoadModule rewrite_module module/mod_ rewrite.so取消注释

　　●修改conf/httpd.conf找到Include conf/extra/httpd-vhosts.conf取消注释

　　●修改conf/extra/httpd-vhosts.conf在最后面增加下面的内容即可

<VirtualHost *:80>
    ServerName b.com
    ErrorLog "logs/b.com-error.log"
    CustomLog "logs/b.com-access.log" common
    ProxyPass / http://localhost:8080/
    # 把请求头的origin值返回到Access-Control-Allow-Origin字段
    Header always set Access-Control-Allow-Origin "expr=%{req:origin}"
    # 把请求头的Access-Control-Allow-Headers值返回到Access-Control-Allow-Headers字段
    Header always Access-Control-Allow-Headers "expr=%{Access-Control-Allow-Headers}"
    Header always set Access-Control-Allow-Methods "*";
    Header always set Access-Control-Max-Age "3600";
    Header always set Access-Control-Allow-Credentials ""true";
    # 处理预检命令OPTIONS，直接返回204
    RewriteEngine On
    RewriteCond %{REQUEST_METHOD}OPTIONS
    RewriteRule ^(.*)$"/" [R=204,L]
</VirtualHost>

Spring框架支持

在类或方法上使用注解@CrossOrigin即可支持跨域

3-4 隐藏跨域

　　●使用Nginx反向代理实现

　　●修改主机hosts文件增加映射本地域名：127.0.0.1 a.com

　　●在vhost目录下创建a.com.conf

　　●启动niginx，访问a.com/ajaxserver/get1

编写a.com.conf

server{
    listen 80;
    server_name a.com;
    location /{
         proxy_pass http://localhost:8081/;
    }
    location /ajaxserver{
         proxy_pass http://localhost:8080/test/;
    }
}

使用Apache反向代理实现

修改conf/extra/httpd-vhosts.conf在最后面增加下面的内容即可

<VirtualHost *:80>
    ServerName a.com
    ErrorLog "logs/a.com-error.log"
    CustomLog "logs/a.com-access.log" common
    ProxyPass / http://localhost:8081/
    ProxyPass /ajaxserverapache http://localhost:8080/test
</VirtualHost>

课程总结

4-1 课程总结

课程总结

　　●产生原因：主要是浏览器对Ajax请求的限制

　　●解决思路：JSONP、支持跨域、隐藏跨域

　　●核心原理：了解Http协议关于跨域方面的规定

　●Solution: Use Filter, Nginx forward and reverse proxy, Apache forward and reverse proxy, Spring framework support

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