Java tutorial
/* * Copyright 2014 the original author or authors. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.springframework.sync.diffsync; import static org.junit.Assert.assertEquals; import static org.junit.Assert.assertFalse; import static org.junit.Assert.assertNotEquals; import static org.junit.Assert.assertNull; import static org.junit.Assert.assertTrue; import static org.junit.Assert.fail; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.util.ArrayList; import java.util.List; import org.junit.After; import org.junit.Test; import org.junit.runner.RunWith; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.core.io.ClassPathResource; import org.springframework.sync.AddOperation; import org.springframework.sync.MoveOperation; import org.springframework.sync.Patch; import org.springframework.sync.PatchException; import org.springframework.sync.PatchOperation; import org.springframework.sync.Person; import org.springframework.sync.Todo; import org.springframework.sync.TodoRepository; import org.springframework.sync.diffsync.shadowstore.MapBasedShadowStore; import org.springframework.sync.json.JsonPatchPatchConverter; import org.springframework.test.context.ContextConfiguration; import org.springframework.test.context.junit4.SpringJUnit4ClassRunner; import org.springframework.transaction.annotation.Transactional; import com.fasterxml.jackson.core.JsonProcessingException; import com.fasterxml.jackson.databind.ObjectMapper; @RunWith(SpringJUnit4ClassRunner.class) @ContextConfiguration(classes = EmbeddedDataSourceConfig.class) @Transactional public class DiffSyncTest { @Autowired private TodoRepository repository; private static final ObjectMapper OBJECT_MAPPER = new ObjectMapper(); @After public void cleanup() { repository.deleteAll(); } // // Apply patches - lists // @Test public void patchList_emptyPatch() throws Exception { DiffSync<Todo> sync = new DiffSync<Todo>(new MapBasedShadowStore("x"), Todo.class); Patch patch = readJsonPatchFromResource("patch-empty"); List<Todo> todos = getTodoList(); List<Todo> patched = sync.apply(todos, patch); assertEquals(patched, getTodoList()); // original remains unchanged assertEquals(todos, getTodoList()); } @Test public void patchList_addNewItem() throws Exception { DiffSync<Todo> sync = new DiffSync<Todo>(new MapBasedShadowStore("x"), Todo.class); Patch patch = readJsonPatchFromResource("patch-add-new-item"); List<Todo> todos = getTodoList(); List<Todo> patched = sync.apply(todos, patch); // original should remain unchanged assertEquals(todos, getTodoList()); assertNotEquals(patched, todos); assertEquals(4, patched.size()); assertEquals(todos.get(0), patched.get(0)); assertEquals(todos.get(1), patched.get(1)); assertEquals(todos.get(2), patched.get(2)); assertEquals(new Todo(null, "D", false), patched.get(3)); } @Test public void patchList_changeSingleEntityStatusAndDescription() throws Exception { DiffSync<Todo> sync = new DiffSync<Todo>(new MapBasedShadowStore("x"), Todo.class); Patch patch = readJsonPatchFromResource("patch-change-single-status-and-desc"); List<Todo> todos = getTodoList(); List<Todo> patched = sync.apply(todos, patch); // original should remain unchanged assertEquals(todos, getTodoList()); assertNotEquals(patched, todos); assertEquals(3, patched.size()); assertEquals(todos.get(0), patched.get(0)); assertEquals(new Todo(2L, "BBB", true), patched.get(1)); assertEquals(todos.get(2), patched.get(2)); } @Test public void patchList_changeSingleEntityStatus() throws Exception { DiffSync<Todo> sync = new DiffSync<Todo>(new MapBasedShadowStore("x"), Todo.class); Patch patch = readJsonPatchFromResource("patch-change-single-status"); List<Todo> todos = getTodoList(); List<Todo> patched = sync.apply(todos, patch); // original should remain unchanged assertEquals(todos, getTodoList()); assertNotEquals(patched, todos); assertEquals(3, patched.size()); assertEquals(todos.get(0), patched.get(0)); assertEquals(new Todo(2L, "B", true), patched.get(1)); assertEquals(todos.get(2), patched.get(2)); } @Test public void patchList_changeStatusAndDeleteTwoItems() throws Exception { DiffSync<Todo> sync = new DiffSync<Todo>(new MapBasedShadowStore("x"), Todo.class); Patch patch = readJsonPatchFromResource("patch-change-status-and-delete-two-items"); List<Todo> todos = getTodoList(); List<Todo> patched = sync.apply(todos, patch); // original should remain unchanged assertEquals(todos, getTodoList()); assertNotEquals(patched, todos); assertEquals(1, patched.size()); assertEquals(new Todo(1L, "A", true), patched.get(0)); } @Test public void patchList_changeTwoStatusAndDescription() throws Exception { DiffSync<Todo> sync = new DiffSync<Todo>(new MapBasedShadowStore("x"), Todo.class); Patch patch = readJsonPatchFromResource("patch-change-two-status-and-desc"); List<Todo> todos = getTodoList(); List<Todo> patched = sync.apply(todos, patch); // original should remain unchanged assertEquals(todos, getTodoList()); assertNotEquals(patched, todos); assertEquals(3, patched.size()); assertEquals(new Todo(1L, "AAA", false), patched.get(0)); assertEquals(new Todo(2L, "B", true), patched.get(1)); assertEquals(new Todo(3L, "C", false), patched.get(2)); } @Test public void patchList_deleteTwoItemsAndChangeStatusOnAnother() throws Exception { DiffSync<Todo> sync = new DiffSync<Todo>(new MapBasedShadowStore("x"), Todo.class); Patch patch = readJsonPatchFromResource("patch-delete-twoitems-and-change-status-on-another"); List<Todo> todos = getTodoList(); List<Todo> patched = sync.apply(todos, patch); // original should remain unchanged assertEquals(todos, getTodoList()); assertNotEquals(patched, todos); assertEquals(1, patched.size()); assertEquals(new Todo(3L, "C", true), patched.get(0)); } @Test public void patchList_patchFailingOperationFirst() throws Exception { DiffSync<Todo> sync = new DiffSync<Todo>(new MapBasedShadowStore("x"), Todo.class); Patch patch = readJsonPatchFromResource("patch-failing-operation-first"); List<Todo> todos = getTodoList(); List<Todo> patched = null; try { patched = sync.apply(todos, patch); fail(); } catch (PatchException e) { // original should remain unchanged assertEquals(todos, getTodoList()); assertNull(patched); } } @Test public void patchList_patchFailingOperationInMiddle() throws Exception { DiffSync<Todo> sync = new DiffSync<Todo>(new MapBasedShadowStore("x"), Todo.class); Patch patch = readJsonPatchFromResource("patch-failing-operation-in-middle"); List<Todo> todos = getTodoList(); List<Todo> patched = null; try { patched = sync.apply(todos, patch); fail(); } catch (PatchException e) { // original should remain unchanged assertEquals(todos, getTodoList()); assertNull(patched); } } @Test public void patchList_manySuccessfulOperations() throws Exception { DiffSync<Todo> sync = new DiffSync<Todo>(new MapBasedShadowStore("x"), Todo.class); Patch patch = readJsonPatchFromResource("patch-many-successful-operations"); List<Todo> todos = getBigTodoList(); List<Todo> patched = sync.apply(todos, patch); // original should remain unchanged assertEquals(todos, getBigTodoList()); assertNotEquals(patched, todos); assertEquals(6, patched.size()); assertEquals(new Todo(1L, "A", true), patched.get(0)); assertEquals(new Todo(2L, "B", true), patched.get(1)); assertEquals(new Todo(3L, "C", false), patched.get(2)); assertEquals(new Todo(4L, "C", false), patched.get(3)); assertEquals(new Todo(1L, "A", true), patched.get(4)); assertEquals(new Todo(5L, "E", false), patched.get(5)); } @Test public void patchList_modifyThenRemoveItem() throws Exception { DiffSync<Todo> sync = new DiffSync<Todo>(new MapBasedShadowStore("x"), Todo.class); Patch patch = readJsonPatchFromResource("patch-modify-then-remove-item"); List<Todo> todos = getTodoList(); List<Todo> patched = sync.apply(todos, patch); // original should remain unchanged assertEquals(todos, getTodoList()); assertNotEquals(patched, todos); assertEquals(2, patched.size()); assertEquals(new Todo(1L, "A", false), patched.get(0)); assertEquals(new Todo(3L, "C", false), patched.get(1)); } @Test public void patchList_removeItem() throws Exception { DiffSync<Todo> sync = new DiffSync<Todo>(new MapBasedShadowStore("x"), Todo.class); Patch patch = readJsonPatchFromResource("patch-remove-item"); List<Todo> todos = getTodoList(); List<Todo> patched = sync.apply(todos, patch); // original should remain unchanged assertEquals(todos, getTodoList()); assertNotEquals(patched, todos); assertEquals(2, patched.size()); assertEquals(new Todo(1L, "A", false), patched.get(0)); assertEquals(new Todo(3L, "C", false), patched.get(1)); } @Test public void patchList_removeTwoItems() throws Exception { DiffSync<Todo> sync = new DiffSync<Todo>(new MapBasedShadowStore("x"), Todo.class); Patch patch = readJsonPatchFromResource("patch-remove-two-items"); List<Todo> todos = getTodoList(); List<Todo> patched = sync.apply(todos, patch); // original should remain unchanged assertEquals(todos, getTodoList()); assertNotEquals(patched, todos); assertEquals(1, patched.size()); assertEquals(new Todo(1L, "A", false), patched.get(0)); } // // Apply patches - single entity // @Test public void patchEntity_emptyPatch() throws Exception { DiffSync<Todo> sync = new DiffSync<Todo>(new MapBasedShadowStore("x"), Todo.class); Patch patch = readJsonPatchFromResource("patch-empty"); Todo todo = new Todo(1L, "A", false); Todo patched = sync.apply(todo, patch); assertEquals(1L, patched.getId().longValue()); assertEquals("A", patched.getDescription()); assertFalse(patched.isComplete()); // original remains unchanged assertEquals(1L, todo.getId().longValue()); assertEquals("A", todo.getDescription()); assertFalse(todo.isComplete()); } @Test public void patchEntity_booleanProperty() throws Exception { DiffSync<Todo> sync = new DiffSync<Todo>(new MapBasedShadowStore("x"), Todo.class); Patch patch = readJsonPatchFromResource("single-change-status"); Todo todo = new Todo(1L, "A", false); Todo patched = sync.apply(todo, patch); assertEquals(1L, patched.getId().longValue()); assertEquals("A", patched.getDescription()); assertTrue(patched.isComplete()); // original remains unchanged assertEquals(1L, todo.getId().longValue()); assertEquals("A", todo.getDescription()); assertFalse(todo.isComplete()); } @Test public void patchEntity_stringProperty() throws Exception { DiffSync<Todo> sync = new DiffSync<Todo>(new MapBasedShadowStore("x"), Todo.class); Patch patch = readJsonPatchFromResource("single-change-description"); Todo todo = new Todo(1L, "A", false); Todo patched = sync.apply(todo, patch); assertEquals(1L, patched.getId().longValue()); assertEquals("AAA", patched.getDescription()); assertFalse(patched.isComplete()); // original remains unchanged assertEquals(1L, todo.getId().longValue()); assertEquals("A", todo.getDescription()); assertFalse(todo.isComplete()); } @Test public void patchEntity_numericProperty() throws Exception { DiffSync<Todo> sync = new DiffSync<Todo>(new MapBasedShadowStore("x"), Todo.class); Patch patch = readJsonPatchFromResource("single-change-id"); Todo todo = new Todo(1L, "A", false); Todo patched = sync.apply(todo, patch); assertEquals(123L, patched.getId().longValue()); assertEquals("A", patched.getDescription()); assertFalse(patched.isComplete()); // original remains unchanged assertEquals(1L, todo.getId().longValue()); assertEquals("A", todo.getDescription()); assertFalse(todo.isComplete()); } @Test public void patchEntity_stringAndBooleanProperties() throws Exception { DiffSync<Todo> sync = new DiffSync<Todo>(new MapBasedShadowStore("x"), Todo.class); Patch patch = readJsonPatchFromResource("single-change-status-and-desc"); Todo todo = new Todo(1L, "A", false); Todo patched = sync.apply(todo, patch); assertEquals(1L, patched.getId().longValue()); assertEquals("BBB", patched.getDescription()); assertTrue(patched.isComplete()); // original remains unchanged assertEquals(1L, todo.getId().longValue()); assertEquals("A", todo.getDescription()); assertFalse(todo.isComplete()); } @Test public void patchEntity_moveProperty() throws Exception { DiffSync<Person> sync = new DiffSync<Person>(new MapBasedShadowStore("x"), Person.class); List<PatchOperation> ops = new ArrayList<PatchOperation>(); ops.add(new MoveOperation("/firstName", "/lastName")); Patch patch = new Patch(ops); Person person = new Person("Edmund", "Blackadder"); Person patched = sync.apply(person, patch); assertEquals("Blackadder", patched.getFirstName()); assertNull(patched.getLastName()); } // // Guaranteed Delivery - Normal operations scenario // @Test public void patchList_addNewItem_normal() throws Exception { DiffSync<Todo> sync = new DiffSync<Todo>(new MapBasedShadowStore("x"), Todo.class); Patch patch = readJsonPatchFromResource("patch-add-new-item"); VersionedPatch versionedPatch = new VersionedPatch(patch.getOperations(), 0, 0); List<Todo> todos = getTodoList(); List<Todo> patched = sync.apply(todos, versionedPatch); VersionedPatch diff = sync.diff(patched); assertEquals(1, diff.getClientVersion()); // the server is acknowledge client version 1 (the client should be at that version by this time) assertEquals(0, diff.getServerVersion()); // the server created the patch against server version 0 (but it will be 1 after the patch is created) // original should remain unchanged assertEquals(todos, getTodoList()); assertNotEquals(patched, todos); assertEquals(4, patched.size()); assertEquals(todos.get(0), patched.get(0)); assertEquals(todos.get(1), patched.get(1)); assertEquals(todos.get(2), patched.get(2)); assertEquals(new Todo(null, "D", false), patched.get(3)); } @Test public void patchEntity_moveProperty_normal() throws Exception { DiffSync<Person> sync = new DiffSync<Person>(new MapBasedShadowStore("x"), Person.class); List<PatchOperation> ops = new ArrayList<PatchOperation>(); ops.add(new MoveOperation("/firstName", "/lastName")); VersionedPatch vPatch1 = new VersionedPatch(ops, 0, 0); Person person = new Person("Edmund", "Blackadder"); Person patched = sync.apply(person, vPatch1); VersionedPatch diff = sync.diff(patched); assertEquals(1, diff.getClientVersion()); // the server is acknowledge client version 1 (the client should be at that version by this time) assertEquals(0, diff.getServerVersion()); // the server created the patch against server version 0 (but it will be 1 after the patch is created) assertEquals("Blackadder", patched.getFirstName()); assertNull(patched.getLastName()); } // // Guaranteed Delivery - Duplicate packet scenario // @Test public void patchList_addNewItem_duplicate() throws Exception { DiffSync<Todo> sync = new DiffSync<Todo>(new MapBasedShadowStore("x"), Todo.class); Patch patch = readJsonPatchFromResource("patch-add-new-item"); VersionedPatch versionedPatch = new VersionedPatch(patch.getOperations(), 0, 0); VersionedPatch versionedPatch2 = new VersionedPatch(patch.getOperations(), 0, 0); List<Todo> todos = getTodoList(); List<Todo> patched = sync.apply(todos, versionedPatch, versionedPatch2); VersionedPatch diff = sync.diff(patched); assertEquals(1, diff.getClientVersion()); // the server is acknowledge client version 1 (the client should be at that version by this time) assertEquals(0, diff.getServerVersion()); // the server created the patch against server version 0 (but it will be 1 after the patch is created) // original should remain unchanged assertEquals(todos, getTodoList()); assertNotEquals(patched, todos); assertEquals(4, patched.size()); assertEquals(todos.get(0), patched.get(0)); assertEquals(todos.get(1), patched.get(1)); assertEquals(todos.get(2), patched.get(2)); assertEquals(new Todo(null, "D", false), patched.get(3)); } @Test public void patchEntity_moveProperty_duplicate() throws Exception { DiffSync<Person> sync = new DiffSync<Person>(new MapBasedShadowStore("x"), Person.class); List<PatchOperation> ops = new ArrayList<PatchOperation>(); ops.add(new MoveOperation("/firstName", "/lastName")); VersionedPatch vPatch1 = new VersionedPatch(ops, 0, 0); VersionedPatch vPatch2 = new VersionedPatch(ops, 0, 0); Person person = new Person("Edmund", "Blackadder"); Person patched = sync.apply(person, vPatch1, vPatch2); VersionedPatch diff = sync.diff(patched); assertEquals(1, diff.getClientVersion()); // the server is acknowledge client version 1 (the client should be at that version by this time) assertEquals(0, diff.getServerVersion()); // the server created the patch against server version 0 (but it will be 1 after the patch is created) assertEquals("Blackadder", patched.getFirstName()); assertNull(patched.getLastName()); } // // Guaranteed Delivery - Lost outbound packet scenario // // TODO: This is primarily a client-side case. By definition, the server never receives the patch. // Therefore, there's nothing server-side to be tested. // However, this case *does* apply to Spring Sync when used in an Android client. // Therefore, tests for this scenario will need to be fleshed out. // // Guaranteed Delivery - Lost return packet scenario // @Test public void patchList_addNewItem_lostReturn() throws Exception { DiffSync<Todo> sync = new DiffSync<Todo>(new MapBasedShadowStore("x"), Todo.class); // Create the list resource List<Todo> todos = getTodoList(); // Apply an initial patch to get the server shadow's client version bumped up. // Initially, the server shadow's server and client versions are both 0, // matching the incoming patch's versions, so the patch is applied normally. List<PatchOperation> ops1 = new ArrayList<PatchOperation>(); ops1.add(new AddOperation("/~", new Todo(100L, "NEW ITEM 100", false))); VersionedPatch versionedPatch = new VersionedPatch(ops1, 0, 0); // At this point, the client sends the patch to the server, the client puts the patch in an outbound stack, // the client increments its shadow client version to 1, and the server calls sync.apply() to apply the patch. List<Todo> patched = sync.apply(todos, versionedPatch); // After the patch is applied, the server shadow versions are // - Primary shadow: serverVersion = 0, clientVersion = 1 // - Backup shadow : serverVersion = 0, clientVersion = 1 // At this point, the server's shadow has client version 1 and server version 0 // The server then copies its current shadow to backup shadow before performing a new diff against the shadow, bumping the server version to 1 *after* the diff is performed. // The backup shadow, having been taken before the new diff was created, still has server version 0. // Before it performs the diff, however, it copies its current shadow to backup shadow. // The diff was performed against the shadow whose client version 1 and server version 0, therefore the patch will have client version 1 and server version 0. VersionedPatch lostDiff = sync.diff(patched); // After the diff is applied, the server shadow's server version is incremented. // - Primary shadow: serverVersion = 1, clientVersion = 1 // - Backup shadow : serverVersion = 0, clientVersion = 1 // Verify that the patch has client version 1, server version 0 assertEquals(1, lostDiff.getClientVersion()); assertEquals(0, lostDiff.getServerVersion()); // In the lost return packet scenario, the client never receives that return diff (lostDiff) or acknowledgement of the server having applied the first patch. // The client can only assume that the server never received it (although it did). // So it produces a new patch against its shadow (whose server version is still at 0 and client version is 1). // It then sends both patches to the server and the server attempts to apply them both. List<PatchOperation> ops2 = new ArrayList<PatchOperation>(); ops2.add(new AddOperation("/~", new Todo(200L, "NEW ITEM 200", false))); VersionedPatch versionedPatch2 = new VersionedPatch(ops2, 0, 1); patched = sync.apply(patched, versionedPatch, versionedPatch2); // The first patch's server version is 0, which is less than the server shadow's server version of 1. // This indicates a lost packet scenario, meaning that the client never received or applied the // return patch from the previous cycle. // So the server resurrects the backup shadow into the primary shadow: // - Primary shadow: serverVersion = 0, clientVersion = 1 // - Backup shadow : serverVersion = 0, clientVersion = 1 // Then it tries to apply the first patch. Since the patch's client version is less than the shadow's client version, // it ignores the patch as a duplicate (that was applied earlier) // Then it tries to apply the second patch. This patch's client version is the same as the shadow's client version, // so it applies it as with normal operation. // After the applying the 2nd patch, the server shadow's server version is incremented. // - Primary shadow: serverVersion = 0, clientVersion = 2 // - Backup shadow : serverVersion = 0, clientVersion = 2 // Finally, the server performs a diff against the shadow (whose server version is 0 and whose client version is 2). // Therefore, the patch produced should have client version 2, server version 0. // After the diff, the server version will be 1, but there's no way to verify that, except to perform another patch. VersionedPatch diff = sync.diff(patched); assertEquals(2, diff.getClientVersion()); // the server is acknowledging client version 1 and 2 (the client should be at that version by this time) assertEquals(0, diff.getServerVersion()); // the server created the patch against server version 0 (but it will be 1 after the patch is created) // After the diff is applied, the server shadow's server version is incremented. // - Primary shadow: serverVersion = 1, clientVersion = 2 // - Backup shadow : serverVersion = 0, clientVersion = 2 // Now test that the resulting list is as expected. // The original should remain unchanged assertEquals(todos, getTodoList()); // The patched resource should now contain 2 additional items, one from each patch sent. // It should *NOT* have two of the item that was added as part of the initial patch (the one that was sent twice). assertNotEquals(patched, todos); assertEquals(5, patched.size()); // Should only have added 2 new items. It shouldn't have added the first new item twice. assertEquals(todos.get(0), patched.get(0)); assertEquals(todos.get(1), patched.get(1)); assertEquals(todos.get(2), patched.get(2)); assertEquals(new Todo(100L, "NEW ITEM 100", false), patched.get(3)); assertEquals(new Todo(200L, "NEW ITEM 200", false), patched.get(4)); } @Test public void patchEntity_moveProperty_lostReturnPacket() throws Exception { DiffSync<Person> sync = new DiffSync<Person>(new MapBasedShadowStore("x"), Person.class); Person person = new Person("Edmund", "Blackadder"); List<PatchOperation> ops1 = new ArrayList<PatchOperation>(); ops1.add(new MoveOperation("/firstName", "/lastName")); VersionedPatch vPatch1 = new VersionedPatch(ops1, 0, 0); Person patched = sync.apply(person, vPatch1); assertEquals("Blackadder", patched.getFirstName()); assertNull(patched.getLastName()); VersionedPatch lostDiff = sync.diff(patched); assertEquals(1, lostDiff.getClientVersion()); assertEquals(0, lostDiff.getServerVersion()); List<PatchOperation> ops2 = new ArrayList<PatchOperation>(); ops2.add(new MoveOperation("/lastName", "/firstName")); VersionedPatch vPatch2 = new VersionedPatch(ops2, 0, 1); patched = sync.apply(patched, vPatch1, vPatch2); VersionedPatch diff = sync.diff(patched); assertEquals(2, diff.getClientVersion()); assertEquals(0, diff.getServerVersion()); assertNull(patched.getFirstName()); assertEquals("Blackadder", patched.getLastName()); } // // private helpers // private List<Todo> getTodoList() { List<Todo> todos = new ArrayList<Todo>(); todos.add(new Todo(1L, "A", false)); todos.add(new Todo(2L, "B", false)); todos.add(new Todo(3L, "C", false)); return todos; } private List<Todo> getBigTodoList() { List<Todo> todos = new ArrayList<Todo>(); todos.add(new Todo(1L, "A", true)); todos.add(new Todo(2L, "B", false)); todos.add(new Todo(3L, "C", false)); todos.add(new Todo(4L, "D", false)); todos.add(new Todo(5L, "E", false)); todos.add(new Todo(6L, "F", false)); return todos; } private Patch readJsonPatchFromResource(String resource) throws IOException, JsonProcessingException { return new JsonPatchPatchConverter().convert(OBJECT_MAPPER.readTree(resource(resource))); } private String resource(String name) throws IOException { ClassPathResource resource = new ClassPathResource("/org/springframework/sync/" + name + ".json"); BufferedReader reader = new BufferedReader(new InputStreamReader(resource.getInputStream())); StringBuilder builder = new StringBuilder(); while (reader.ready()) { builder.append(reader.readLine()); } return builder.toString(); } }