java在http请求中使用CORS

Question

今天，我有以下问题。我想向rest api发出http请求，但我只收到一个405错误。我搜索了一下，发现api使用cors。 那么我如何使用cors发出http请求呢

这是我的http客户端：

package community.opencode.minetools4j.util.http;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NonNull;
import org.apache.commons.io.IOUtils;

import java.io.DataOutputStream;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;
import java.util.HashMap;
import java.util.Map;

/**
 * This is an utility class.
 * It simplify making HTTP requests
 */
public class HttpRequest {

    /**
     * Performs a new HTTP request
     *
     * @param requestBuilder See {@link RequestBuilder}
     * @return See {@link RequestResponse}
     * @throws IOException Will be thrown if the request can't be executed
     */
    public static RequestResponse performRequest(RequestBuilder requestBuilder) throws IOException {
        URL newUrl = new URL(requestBuilder.getPath());

        HttpURLConnection connection = (HttpURLConnection) newUrl.openConnection();
        connection.setRequestMethod(requestBuilder.getMethod().getType());
        requestBuilder.getHeaders().forEach(connection::setRequestProperty);
        connection.setConnectTimeout(5000);
        connection.setReadTimeout(5000);
        connection.setDoOutput(true);

        DataOutputStream out = new DataOutputStream(connection.getOutputStream());
        out.writeBytes(getParametersString(requestBuilder.getParams()));

        int status = connection.getResponseCode();
        String result = IOUtils.toString(connection.getInputStream(), "UTF-8");
        String contentType = connection.getHeaderField("Content-Type");
        connection.getInputStream().close();
        connection.disconnect();
        return new RequestResponse(status, result, contentType);
    }

    /**
     * Makes from a map a valid HTTP string
     * Example: "myField=Hey!&myPassword=abc"
     *
     * @param params The parameters
     * @return The formed String
     * @throws UnsupportedEncodingException Should never be thrown
     */
    private static String getParametersString(Map<String, String> params) throws UnsupportedEncodingException {
        StringBuilder builder = new StringBuilder();
        for (Map.Entry<String, String> entry : params.entrySet()) {
            builder.append(URLEncoder.encode(entry.getKey(), "UTF-8"));
            builder.append("=");
            builder.append(URLEncoder.encode(entry.getValue(), "UTF-8"));
            builder.append("&");
        }
        String result = builder.toString();
        return result.length() > 0 ? result.substring(0, result.length() - 1) : result;
    }

    /**
     * A simple builder class for {@link #performRequest(RequestBuilder)}
     */
    @Data
    public static class RequestBuilder {

        private final String path;
        private final HttpRequestMethod method;

        private final Map<String, String> params = new HashMap<>();
        private final Map<String, String> headers = new HashMap<>();

        public RequestBuilder addParam(@NonNull String name, @NonNull String value) {
            this.params.put(name, value);
            return this;
        }

        public RequestBuilder addHeader(@NonNull String name, @NonNull String value) {
            this.headers.put(name, value);
            return this;
        }
    }

    /**
     * A simplified http response.
     * Including status, message and the returned content type
     */
    @Data
    @AllArgsConstructor
    public static class RequestResponse {

        private int status;
        private String resultMessage;
        private String contentType;
    }
}

package community.opencode.minetools4j.util.http;

import lombok.Getter;

/**
 * Simple enum for {@link HttpRequest}.
 * It's a better way than just write manually the method name
 */
public enum HttpRequestMethod {
    POST("POST"),
    GET("GET"),
    PUT("PUT"),
    HEAD("HEAD"),
    OPTIONS("OPTIONS"),
    DELETE("DELETE"),
    TRACE("TRACE");

    @Getter
    private String type;

    HttpRequestMethod(String type) {
        this.type = type;
    }
}

下面是我发出http请求的方法：

HttpRequest.RequestResponse requestResponse = HttpRequest.performRequest(new HttpRequest.RequestBuilder(API_URI + "/ping/" + host + "/" + port, HttpRequestMethod.GET));

谢谢大家的关注

真诚地， 斯凯莱格

对不起，我英语不好。我希望你能理解我；）

Answer 1

如果您遇到此类错误：

Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:4200' is therefore not allowed access. The response had HTTP status code 405.

您必须创建一个servlet过滤器，并在doFilter方法上添加下面的代码

    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain chain)
        throws IOException, ServletException {
    HttpServletRequest request = (HttpServletRequest) servletRequest;

    HttpServletResponse resp = (HttpServletResponse) servletResponse;
    resp.addHeader("Access-Control-Allow-Origin", "*");
    resp.addHeader("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE,HEAD");
    resp.addHeader("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
    resp.addHeader("Accept-Encoding", "multipart/form-data");

    if (request.getMethod().equals("OPTIONS")) {
        resp.setStatus(200);
        return;
    }
    chain.doFilter(request, servletResponse);
  }

Answer 2

什么是HTTP代码405

状态405表示您发送的请求不允许您使用的方法

Source

如何修复

您需要检查API文档，看看是否有以下错误：

• 缺少身份验证头
• 缺少内容
• 错误的网址
• 错误的方法

简化代码

使用unirest可以简化您的请求代码，并覆盖边缘情况