test(http): pin the URL-query-only contract of ListExchangesServlet

ListExchangesServlet.doPost reads visible and int64_as_string from the
URL query, not from the JSON body -- a counter-intuitive shape shared
only by GetChainParametersServlet. Without a test, a future refactor
that "normalizes" this POST path to read from the body would silently
break clients that pass the flag via the URL.

Author: waynercheung

framework/src/test/java/org/tron/core/services/http/ListExchangesServletTest.java

@@ -0,0 +1,111 @@
+package org.tron.core.services.http;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
+
+import com.alibaba.fastjson.JSON;
+import com.alibaba.fastjson.JSONObject;
+import java.io.UnsupportedEncodingException;
+import javax.annotation.Resource;
+import org.junit.Test;
+import org.springframework.mock.web.MockHttpServletRequest;
+import org.springframework.mock.web.MockHttpServletResponse;
+import org.tron.common.BaseTest;
+import org.tron.common.TestConstants;
+import org.tron.core.config.args.Args;
+
+/**
+ * Integration tests for ListExchangesServlet. This servlet is the canonical example of the
+ * "doGet-delegates-to-doPost, doPost reads URL query (not body)" shape: its doPost calls
+ * Util.getVisible(request) and Util.getInt64AsString(request) instead of PostParams. The
+ * tests below pin that contract so a future refactor that "normalizes" the POST path to
+ * read from the body (as most other servlets do) will fail visibly rather than silently
+ * breaking clients that pass the flag via URL query.
+ *
+ * <p>ExchangeList may be empty on the test DB, so item-level assertions are defensive:
+ * they verify int64 quoting shape only when exchange_id is present in the response.
+ */
+public class ListExchangesServletTest extends BaseTest {
+
+  @Resource(name = "listExchangesServlet")
+  private ListExchangesServlet servlet;
+
+  static {
+    Args.setParam(
+        new String[]{
+            "--output-directory", dbPath(),
+        }, TestConstants.TEST_CONF
+    );
+  }
+
+  private MockHttpServletRequest createPostJsonRequest(String body) {
+    MockHttpServletRequest request = new MockHttpServletRequest();
+    request.setMethod("POST");
+    request.setContentType("application/json");
+    request.setCharacterEncoding("UTF-8");
+    if (body != null) {
+      request.setContent(body.getBytes());
+    }
+    return request;
+  }
+
+  @Test
+  public void testPostWithQueryInt64AsStringTrue() {
+    MockHttpServletRequest request = createPostJsonRequest(null);
+    request.addParameter("int64_as_string", "true");
+    MockHttpServletResponse response = new MockHttpServletResponse();
+    servlet.doPost(request, response);
+    try {
+      String content = response.getContentAsString();
+      assertNotNull("expected valid JSON, got: " + content, JSON.parseObject(content));
+      if (content.contains("\"exchange_id\"")) {
+        assertTrue("exchange_id should be quoted when URL query carries int64_as_string=true, "
+                + "got: " + content,
+            content.matches("(?s).*\"exchange_id\"\\s*:\\s*\"\\d+\".*"));
+      }
+    } catch (UnsupportedEncodingException e) {
+      fail(e.getMessage());
+    }
+  }
+
+  @Test
+  public void testPostBodyFlagIsIgnored() {
+    // Contract: ListExchangesServlet.doPost reads only URL query, mirroring how the same
+    // servlet reads `visible`. A body-only flag must NOT take effect. Breaking this
+    // behavior would be a silent regression for clients that pass the flag via URL.
+    String body = "{\"int64_as_string\": true}";
+    MockHttpServletRequest request = createPostJsonRequest(body);
+    MockHttpServletResponse response = new MockHttpServletResponse();
+    servlet.doPost(request, response);
+    try {
+      String content = response.getContentAsString();
+      assertNotNull("expected valid JSON, got: " + content, JSON.parseObject(content));
+      if (content.contains("\"exchange_id\"")) {
+        assertFalse("body-only int64_as_string must be ignored on this servlet, got: " + content,
+            content.matches("(?s).*\"exchange_id\"\\s*:\\s*\"\\d+\".*"));
+      }
+    } catch (UnsupportedEncodingException e) {
+      fail(e.getMessage());
+    }
+  }
+
+  @Test
+  public void testPostDefaultKeepsNumbers() {
+    MockHttpServletRequest request = createPostJsonRequest(null);
+    MockHttpServletResponse response = new MockHttpServletResponse();
+    servlet.doPost(request, response);
+    try {
+      String content = response.getContentAsString();
+      JSONObject result = JSON.parseObject(content);
+      assertNotNull("expected valid JSON, got: " + content, result);
+      if (content.contains("\"exchange_id\"")) {
+        assertFalse("default behavior must not quote exchange_id, got: " + content,
+            content.matches("(?s).*\"exchange_id\"\\s*:\\s*\"\\d+\".*"));
+      }
+    } catch (UnsupportedEncodingException e) {
+      fail(e.getMessage());
+    }
+  }
+}