[Add] Pixiv 添加一组与 Pixiv 登录会话相关的类;

[Add] PixivLogin, PixivLoginException 初版的登录器接口;
[Add] PixivSession, BasicPixivSession Pixiv 帐号登录会话抽象类和一个默认基本实现;
[Add] ObjectInputStreamLogin 通过反序列化 CacheStore 进行登录的登录器;

ContentGrabbingJi-pixiv/src/main/java/net/lamgc/pixiv/BasicPixivSession.java

@@ -0,0 +1,70 @@
+/*
+ * Copyright (C) 2020  LamGC
+ *
+ * ContentGrabbingJi is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * ContentGrabbingJi is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package net.lamgc.pixiv;
+
+import com.google.common.net.HttpHeaders;
+import org.apache.http.HttpResponse;
+import org.apache.http.client.CookieStore;
+import org.apache.http.client.HttpClient;
+import org.apache.http.client.methods.HttpGet;
+
+import java.io.IOException;
+
+/**
+ * 基本的 Pixiv 会话对象.
+ * @author LamGC
+ */
+public class BasicPixivSession extends PixivSession {
+
+    private final static String PIXIV_LOGOUT_URL = "https://www.pixiv.net/logout.php";
+    private final HttpClient httpClient;
+    private boolean login = true;
+
+    /**
+     * 构造一个会话对象.
+     * @param cookieStore 会话 Cookies.
+     * @param httpClient 用于请求登出的 HttpClient 对象.
+     */
+    public BasicPixivSession(CookieStore cookieStore, HttpClient httpClient) {
+        super(cookieStore);
+        this.httpClient = httpClient;
+    }
+
+    @Override
+    public boolean logOut() throws IOException {
+        HttpGet request = new HttpGet(PIXIV_LOGOUT_URL);
+        StringBuilder builder = new StringBuilder();
+        getCookies().getCookies().forEach(cookie ->
+                builder.append(cookie.getName()).append("=").append(cookie.getValue()).append("; "));
+        request.addHeader(HttpHeaders.COOKIE, builder.toString());
+
+        HttpResponse response = httpClient.execute(request);
+        final int httpRedirectCode = 302;
+        if (response.getStatusLine().getStatusCode() == httpRedirectCode) {
+            login = false;
+            return true;
+        }
+        return false;
+    }
+
+    @Override
+    public boolean isLogin() {
+        return login;
+    }
+
+}