解決Access-Control-Allow-Origin跨域問題

說明：本次的測試環境是一台電腦，啟動兩個springboot應用，如果是其它情況，可能稍有不同，發現時在補充吧。

方法一：給response設置header

public User getUser(HttpServletResponse response) {
    response.setHeader("Access-Control-Allow-Origin","*");
    User user = new User(1,"張三",20);
    return user;
}

方法二：添加注解，如果添加到類上，那么整個類中的方法都可以跨域訪問

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

方法三：在攔截器中設置response的header，以下是springboot中的寫法

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：實現WebMvcConfigurer接口，重寫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");
    }
}