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Posted to notifications@shardingsphere.apache.org by zh...@apache.org on 2022/04/25 13:36:55 UTC
[shardingsphere] branch master updated: Add code formatting blog (#17101)
This is an automated email from the ASF dual-hosted git repository.
zhangliang pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/shardingsphere.git
The following commit(s) were added to refs/heads/master by this push:
new 0600b272b9b Add code formatting blog (#17101)
0600b272b9b is described below
commit 0600b272b9b457bdaf000ad765cad48a21abd304
Author: 龙台 Long Tai <77...@users.noreply.github.com>
AuthorDate: Mon Apr 25 21:36:47 2022 +0800
Add code formatting blog (#17101)
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+title = "Apache ShardingSphere 代码格式化实战 —— Spotless"
+weight = 39
+chapter = true
++++
+
+为什么要代码格式化？代码格式化的意义是让代码更加 **易读易懂易修改**。
+
+ShardingSphere 作为 Apache 顶级开源项目，截止当前已有 380+ 贡献者。因为大部分开发人员的代码风格不一致，在 Github 多人协作的模式下，不易保障项目整体代码格式。
+
+基于以上诉求，ShardingSphere 采用了 [Spotless](https://github.com/diffplug/spotless/tree/main/plugin-maven) 充当代码格式统一的角色。
+
+## 什么是 Spotless
+
+Spotless 是支持多种语言的代码格式化工具，支持 Maven 和 Gradle 以 Plugin 的形式构建。
+
+Spotless 对开发者来说，有 2 种使用方式：检查代码是否存在格式问题，以及格式化代码。
+
+> ShardingSphere 采用 Maven 构建项目，以下若无特殊声明，Spotless 使用 Maven 做演示。
+
+## 如何使用
+
+下述代码是 Spotless 官方示例。
+
+```shell
+user@machine repo % mvn spotless:check
+[ERROR] > The following files had format violations:
+[ERROR] src\main\java\com\diffplug\gradle\spotless\FormatExtension.java
+[ERROR] -\t\t····if·(targets.length·==·0)·{
+[ERROR] +\t\tif·(targets.length·==·0)·{
+[ERROR] Run 'mvn spotless:apply' to fix these violations.
+user@machine repo % mvn spotless:apply
+[INFO] BUILD SUCCESS
+user@machine repo % mvn spotless:check
+[INFO] BUILD SUCCESS
+```
+
+通过 `mvn spotless:check` 检查项目代码时发现错误，接着使用 `mvn spotless:apply` 进行代码格式化；再次检查时，格式化错误消失。
+
+### 1. 项目实战
+
+ShardingSphere 使用 Spotless 实现了添加 **Java 文件 licenseHeader** 和 **Java 代码格式化**。
+
+Spotless 有多种 Java 代码格式化方式，例如：googleJavaFormat、eclipse、prettier 等。基于定制化的考虑，最终采用 eclipse 进行 Java 代码格式化。
+
+
+
+1）根据项目需求添加 licenseHeader
+
+```java
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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.
+ */
+
+
+```
+
+注意，licenseHeader **最后要留有一行空格**。不然 licenseHeader 和 package 之间将没有空隙。
+
+2）添加 shardingsphere_eclipse_formatter.xml
+
+```java
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<!--
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you 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.
+ */
+-->
+<profiles version="13">
+ <profile kind="CodeFormatterProfile" name="'ShardingSphere Apache Current'" version="13">
+ <setting id="org.eclipse.jdt.core.compiler.source" value="1.8"/>
+ <setting id="org.eclipse.jdt.core.compiler.compliance" value="1.8"/>
+ <setting id="org.eclipse.jdt.core.compiler.codegen.targetPlatform" value="1.8"/>
+ <setting id="org.eclipse.jdt.core.formatter.indent_empty_lines" value="true"/>
+ <setting id="org.eclipse.jdt.core.formatter.tabulation.size" value="4"/>
+ <setting id="org.eclipse.jdt.core.formatter.lineSplit" value="200"/>
+ <setting id="org.eclipse.jdt.core.formatter.comment.line_length" value="200"/>
+ <setting id="org.eclipse.jdt.core.formatter.tabulation.char" value="space"/>
+ <setting id="org.eclipse.jdt.core.formatter.indentation.size" value="1"/>
+ <setting id="org.eclipse.jdt.core.formatter.comment.format_javadoc_comments" value="false"/>
+ <setting id="org.eclipse.jdt.core.formatter.join_wrapped_lines" value="false"/>
+ <setting id="org.eclipse.jdt.core.formatter.insert_space_before_colon_in_conditional" value="insert"/>
+ <setting id="org.eclipse.jdt.core.formatter.insert_space_before_colon_in_default" value="do not insert"/>
+ <setting id="org.eclipse.jdt.core.formatter.alignment_for_enum_constants" value="16"/>
+ <setting id="org.eclipse.jdt.core.formatter.insert_space_before_colon_in_labeled_statement" value="do not insert"/>
+ <setting id="org.eclipse.jdt.core.formatter.insert_space_before_colon_in_case" value="do not insert"/>
+ <setting id="org.eclipse.jdt.core.formatter.alignment_for_conditional_expression" value="80"/>
+ <setting id="org.eclipse.jdt.core.formatter.alignment_for_assignment" value="16"/>
+ <setting id="org.eclipse.jdt.core.formatter.blank_lines_after_package" value="1"/>
+ <setting id="org.eclipse.jdt.core.formatter.continuation_indentation_for_array_initializer" value="2"/>
+ <setting id="org.eclipse.jdt.core.formatter.alignment_for_resources_in_try" value="160"/>
+ <setting id="org.eclipse.jdt.core.formatter.alignment_for_throws_clause_in_method_declaration" value="10"/>
+ <setting id="org.eclipse.jdt.core.formatter.alignment_for_parameters_in_method_declaration" value="106"/>
+ <setting id="org.eclipse.jdt.core.formatter.alignment_for_parameters_in_constructor_declaration" value="106"/>
+ <setting id="org.eclipse.jdt.core.formatter.alignment_for_throws_clause_in_constructor_declaration" value="106"/>
+ <setting id="org.eclipse.jdt.core.formatter.alignment_for_arguments_in_explicit_constructor_call.count_dependent" value="16|5|80"/>
+ </profile>
+</profiles>
+```
+
+> ShardingSphere 最新规则查看 [shardingsphere_eclipse_formatter.xml](https://github.com/apache/shardingsphere/blob/master/src/resources/shardingsphere_eclipse_formatter.xml)，另提供一份 [eclipse-java-google-style.xml](https://github.com/google/styleguide/blob/gh-pages/eclipse-java-google-style.xml) 供参考
+
+shardingsphere_eclipse_formatter.xml 的内容是根据 ShardingSphere 代码规范定制开发的，可灵活变动。
+
+3）添加 Maven plugin
+
+```xml
+<plugin>
+ <groupId>com.diffplug.spotless</groupId>
+ <artifactId>spotless-maven-plugin</artifactId>
+ <version>2.22.1</version>
+ <configuration>
+ <java>
+ <eclipse>
+ <file>${maven.multiModuleProjectDirectory}/src/resources/shardingsphere_eclipse_formatter.xml</file>
+ </eclipse>
+ <licenseHeader>
+ <file>${maven.multiModuleProjectDirectory}/src/resources/license-header</file>
+ </licenseHeader>
+ </java>
+ </configuration>
+</plugin>
+```
+
+Spotless 支持格式化指定目录，以及排除指定目录的功能，详情参考 [plugin-maven#java](https://github.com/diffplug/spotless/tree/main/plugin-maven#java)。如无指定，执行 check 或 apply 时，默认项目全量代码。
+
+4）执行代码格式化
+
+执行完上述三个步骤，就可以在项目中执行命令，检查 Java 代码是否符合规范，以及代码格式化功能。
+
+```shell
+user@machine repo % mvn spotless:apply
+[INFO] BUILD SUCCESS
+user@machine repo % mvn spotless:check
+[INFO] BUILD SUCCESS
+```
+
+### 2. 绑定 Maven 生命周期
+
+在 ShardingSphere 实际应用中，选择将 Spotless apply 绑定到 compile 阶段，这样本地执行 mvn install 时就能自动格式化。
+
+```xml
+<plugin>
+ <groupId>com.diffplug.spotless</groupId>
+ <artifactId>spotless-maven-plugin</artifactId>
+ <version>2.22.1</version>
+ <configuration>
+ <java>
+ <eclipse>
+ <file>${maven.multiModuleProjectDirectory}/src/resources/shardingsphere_eclipse_formatter.xml</file>
+ </eclipse>
+ <licenseHeader>
+ <file>${maven.multiModuleProjectDirectory}/src/resources/license-header</file>
+ </licenseHeader>
+ </java>
+ </configuration>
+ <executions>
+ <execution>
+ <goals>
+ <goal>apply</goal>
+ </goals>
+ <phase>compile</phase>
+ </execution>
+ </executions>
+</plugin>
+```
+
+### 3. IDEA 格式化
+
+开发者如果在写代码过程中，想检查单个文件是否符合规范，执行 `mvn spotless:check` 或 `mvn spotless:apply` 显得有些笨重，因为格式化范围默认是整个项目。
+
+我们可以使用 shardingsphere_eclipse_formatter.xml 替换 IntelliJ IDEA 原有格式化功能，这样在写代码过程中可以随时格式化，极大提升了开发效率。
+
+> IDEA 版本 2019.3.4。
+
+1）安装插件 Eclipse Code Formatter
+
+
+
+2）选择 shardingsphere_eclipse_formatter.xml 为默认格式化模板
+
+
+
+使用 IDEA 代码格式化快捷键，就可以完成 Spotless 代码格式化。
+
+## 常见问题
+
+### 1. Spotless 与 Checkstyle 冲突
+
+[Checkstyle](https://github.com/checkstyle/checkstyle) 是一种用于检查 Java 源代码是否符合代码标准或一组验证规则（最佳实践）的工具。
+
+极端场景下，Spotless 格式化代码后，通过 Checkstyle 检查代码会不通过。
+
+根本原因在于两者设定的检查配置和格式化配置冲突。举个例子，Spotless 格式化后换行缩进了 16 个空格，而 Checkstyle 的换行检查是 12 个空格。
+
+```java
+private static Collection<PreciseHintShadowValue<Comparable<?>>> createNoteShadowValues(final ShadowDetermineCondition shadowDetermineCondition) {
+ // Checkstyle 可以通过的格式
+ return shadowDetermineCondition.getSqlComments().stream().<PreciseHintShadowValue<Comparable<?>>>map(
+ each -> new PreciseHintShadowValue<>(tableName, shadowOperationType, each)).collect(Collectors.toList());
+ // Spotless 格式化后
+ return shadowDetermineCondition.getSqlComments().stream().<PreciseHintShadowValue<Comparable<?>>>map(
+ each -> new PreciseHintShadowValue<>(tableName, shadowOperationType, each)).collect(Collectors.toList());
+}
+```
+
+这种情况，需要开发者衡量如何取舍。解决方案有两种：修改 Spotless 的格式化规则，或修改 Checkstyle 的检查规则。
+
+### 2. CRLF 与 LF 格式化冲突
+
+参考 https://github.com/diffplug/spotless/issues/1171
+
+## 文末总结
+
+文章介绍了 Apache ShardingSphere 使用 Spotless 完成历史代码格式化，以及后续代码格式的统一，对项目代码的整洁起到了很大帮助。
+
+当然，Spotless 的功能不止 Java 代码的格式化，包括不限于 Pom 和 Markdown 等文件类型的格式化，后续这些都会在 ShardingSphere 得以应用。
+
+## 作者简介
+
+龙台，Apache ShardingSphere Contributor，Github 2.2k star hippo4j 作者，Github ID：longtai-cn。
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