解决Access-Control-Allow-Origin跨域问题

说明：本次的测试环境是一台电脑，启动两个springboot应用，如果是其它情况，可能稍有不同，发现时在补充吧。

方法一：给response设置header

public User getUser(HttpServletResponse response) {
    response.setHeader("Access-Control-Allow-Origin","*");
    User user = new User(1,"张三",20);
    return user;
}

方法二：添加注解，如果添加到类上，那么整个类中的方法都可以跨域访问

@CrossOrigin
public User getUser2(HttpServletResponse response) {
    User user = new User(2,"李四",20);
    return user;
}

方法三：在拦截器中设置response的header，以下是springboot中的写法

public class WebInterceptor implements HandlerInterceptor{

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
            throws Exception {
        response.setHeader("Access-Control-Allow-Origin","*");
        return true;
    }
}

@Configuration
public class MyWebMvcConfigurer implements WebMvcConfigurer{

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new WebInterceptor());        
    }
}

方法四：实现WebMvcConfigurer接口，重写addCorsMappings方法，如下：

@Configuration
public class MyWebMvcConfigurer implements WebMvcConfigurer{

    @Override
    public void addCorsMappings(CorsRegistry registry) {
        registry.addMapping("/**")
        .allowedOrigins("*")
        .allowCredentials(true)
        .allowedMethods("GET","POST","PUT","DELETE","HEAD");
    }
}