如何使用Java封装REST请求工具类 Java通用网络请求封装示例

import okhttp3.*;
import java.io.IOException;
import java.util.Map;
import java.util.concurrent.TimeUnit;
import com.fasterxml.jackson.databind.ObjectMapper; // 用于JSON序列化/反序列化

public class RestApiClient {

    private static final MediaType JSON_MEDIA_TYPE = MediaType.get("application/json; charset=utf-8");
    private final OkHttpClient client;
    private final ObjectMapper objectMapper;

    /**
     * 默认构造函数，使用预设的超时时间创建OkHttpClient实例
     * 和默认的ObjectMapper。
     */
    public RestApiClient() {
        this.client = new OkHttpClient.Builder()
                .connectTimeout(10, TimeUnit.SECONDS) // 连接超时
                .readTimeout(30, TimeUnit.SECONDS)    // 读取超时
                .writeTimeout(30, TimeUnit.SECONDS)   // 写入超时
                .build();
        this.objectMapper = new ObjectMapper();
    }

    /**
     * 允许外部传入自定义的OkHttpClient和ObjectMapper实例，
     * 提升灵活性和可测试性。
     * @param customClient 自定义的OkHttpClient
     * @param customMapper 自定义的ObjectMapper
     */
    public RestApiClient(OkHttpClient customClient, ObjectMapper customMapper) {
        this.client = customClient;
        this.objectMapper = customMapper;
    }

    /**
     * 发送GET请求。
     * @param url 请求URL
     * @param headers 请求头，可为null
     * @param queryParams 查询参数，可为null
     * @return 响应体字符串
     * @throws IOException 网络或IO错误
     * @throws HttpRequestException HTTP请求失败（非2xx状态码）
     */
    public String get(String url, Map<String, String> headers, Map<String, String> queryParams) throws IOException, HttpRequestException {
        HttpUrl.Builder urlBuilder = HttpUrl.parse(url).newBuilder();
        if (queryParams != null) {
            queryParams.forEach(urlBuilder::addQueryParameter);
        }

        Request.Builder requestBuilder = new Request.Builder().url(urlBuilder.build());
        if (headers != null) {
            headers.forEach(requestBuilder::addHeader);
        }

        try (Response response = client.newCall(requestBuilder.build()).execute()) {
            return handleResponse(response);
        }
    }

    /**
     * 发送POST请求，请求体为JSON格式。
     * @param url 请求URL
     * @param headers 请求头，可为null
     * @param bodyObj 请求体对象，将被序列化为JSON
     * @return 响应体字符串
     * @throws IOException 网络或IO错误，或JSON序列化错误
     * @throws HttpRequestException HTTP请求失败（非2xx状态码）
     */
    public String postJson(String url, Map<String, String> headers, Object bodyObj) throws IOException, HttpRequestException {
        String jsonBody = objectMapper.writeValueAsString(bodyObj);
        RequestBody requestBody = RequestBody.create(jsonBody, JSON_MEDIA_TYPE);

        Request.Builder requestBuilder = new Request.Builder().url(url).post(requestBody);
        if (headers != null) {
            headers.forEach(requestBuilder::addHeader);
        }

        try (Response response = client.newCall(requestBuilder.build()).execute()) {
            return handleResponse(response);
        }
    }

    /**
     * 发送PUT请求，请求体为JSON格式。
     * @param url 请求URL
     * @param headers 请求头，可为null
     * @param bodyObj 请求体对象，将被序列化为JSON