了解gradlew和gradle命令的区别之前，尝试花几分钟思考下面几个问题：

• gradlew是一个什么命令工具呢？
• 为什么要有这个工具？
• gradlew脚本是怎样的？
• gradlew命令和gradle命令的区别？

一、gradlew、gradle脚本的区别

先看看gradlew脚本代码

#!/usr/bin/env sh

PRG="$0"
# 1.检查是否是软连接
while [ -h "$PRG" ] ; do
    ls=`ls -ld "$PRG"`
    link=`expr "$ls" : '.*-> \(.*\)$'`
    if expr "$link" : '/.*' > /dev/null; then
        PRG="$link"
    else
        PRG=`dirname "$PRG"`"/$link"
    fi
done
SAVED="`pwd`"
cd "`dirname \"$PRG\"`/" >/dev/null
APP_HOME="`pwd -P`"
cd "$SAVED" >/dev/null

APP_NAME="Gradle"
APP_BASE_NAME=`basename "$0"`

# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
DEFAULT_JVM_OPTS=""

# Use the maximum available, or set MAX_FD != -1 to use that value.
MAX_FD="maximum"

warn () {
    echo "$*"
}

die () {
    echo
    echo "$*"
    echo
    exit 1
}

# 2.获取系统内核信息
cygwin=false
msys=false
darwin=false
nonstop=false
case "`uname`" in
  CYGWIN* )
    cygwin=true
    ;;
  Darwin* )
    darwin=true
    ;;
  MINGW* )
    msys=true
    ;;
  NONSTOP* )
    nonstop=true
    ;;
esac

# 3.设置classpath路径
CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar

# Determine the Java command to use to start the JVM.
if [ -n "$JAVA_HOME" ] ; then
    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
        # IBM's JDK on AIX uses strange locations for the executables
        JAVACMD="$JAVA_HOME/jre/sh/java"
    else
        JAVACMD="$JAVA_HOME/bin/java"
    fi
    if [ ! -x "$JAVACMD" ] ; then
        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME

Please set the JAVA_HOME variable in your environment to match the
location of your Java installation."
    fi
else
    JAVACMD="java"
    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.

Please set the JAVA_HOME variable in your environment to match the
location of your Java installation."
fi

# Increase the maximum file descriptors if we can.
if [ "$cygwin" = "false" -a "$darwin" = "false" -a "$nonstop" = "false" ] ; then
    MAX_FD_LIMIT=`ulimit -H -n`
    if [ $? -eq 0 ] ; then
        if [ "$MAX_FD" = "maximum" -o "$MAX_FD" = "max" ] ; then
            MAX_FD="$MAX_FD_LIMIT"
        fi
        ulimit -n $MAX_FD
        if [ $? -ne 0 ] ; then
            warn "Could not set maximum file descriptor limit: $MAX_FD"
        fi
    else
        warn "Could not query maximum file descriptor limit: $MAX_FD_LIMIT"
    fi
fi

# For Darwin, add options to specify how the application appears in the dock
if $darwin; then
    GRADLE_OPTS="$GRADLE_OPTS \"-Xdock:name=$APP_NAME\" \"-Xdock:icon=$APP_HOME/media/gradle.icns\""
fi

# For Cygwin, switch paths to Windows format before running java
if $cygwin ; then
    APP_HOME=`cygpath --path --mixed "$APP_HOME"`
    CLASSPATH=`cygpath --path --mixed "$CLASSPATH"`
    JAVACMD=`cygpath --unix "$JAVACMD"`

    # We build the pattern for arguments to be converted via cygpath
    ROOTDIRSRAW=`find -L / -maxdepth 1 -mindepth 1 -type d 2>/dev/null`
    SEP=""
    for dir in $ROOTDIRSRAW ; do
        ROOTDIRS="$ROOTDIRS$SEP$dir"
        SEP="|"
    done
    OURCYGPATTERN="(^($ROOTDIRS))"
    # Add a user-defined pattern to the cygpath arguments
    if [ "$GRADLE_CYGPATTERN" != "" ] ; then
        OURCYGPATTERN="$OURCYGPATTERN|($GRADLE_CYGPATTERN)"
    fi
    # Now convert the arguments - kludge to limit ourselves to /bin/sh
    i=0
    for arg in "$@" ; do
        CHECK=`echo "$arg"|egrep -c "$OURCYGPATTERN" -`
        CHECK2=`echo "$arg"|egrep -c "^-"`                                 ### Determine if an option

        if [ $CHECK -ne 0 ] && [ $CHECK2 -eq 0 ] ; then                    ### Added a condition
            eval `echo args$i`=`cygpath --path --ignore --mixed "$arg"`
        else
            eval `echo args$i`="\"$arg\""
        fi
        i=$((i+1))
    done
    case $i in
        (0) set -- ;;
        (1) set -- "$args0" ;;
        (2) set -- "$args0" "$args1" ;;
        (3) set -- "$args0" "$args1" "$args2" ;;
        (4) set -- "$args0" "$args1" "$args2" "$args3" ;;
        (5) set -- "$args0" "$args1" "$args2" "$args3" "$args4" ;;
        (6) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" ;;
        (7) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" ;;
        (8) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" ;;
        (9) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" "$args8" ;;
    esac
fi

# Escape application args
save () {
    for i do printf %s\\n "$i" | sed "s/'/'\\\\''/g;1s/^/'/;\$s/\$/' \\\\/" ; done
    echo " "
}
APP_ARGS=$(save "$@")

# Collect all arguments for the java command, following the shell quoting and substitution rules
eval set -- $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS "\"-Dorg.gradle.appname=$APP_BASE_NAME\"" -classpath "\"$CLASSPATH\"" org.gradle.wrapper.GradleWrapperMain "$APP_ARGS"

# by default we should be in the correct project dir, but when run from Finder on Mac, the cwd is wrong
if [ "$(uname)" = "Darwin" ] && [ "$HOME" = "$PWD" ]; then
  cd "$(dirname "$0")"
fi

# 4.执行java命令运行wrapper jar包里头的类文件
exec "$JAVACMD" "$@"

代码量不多，脚本主要干了几件事：

获取电脑系统内核的信息，JRE环境信息等；

设置classpath路径；

执行java命令工具，调用gradle jar包的class文件

在gradlew脚本中添加log打印：

echo "$JAVACMD $@"

$ ./gradlew -v
/Library/Java/JavaVirtualMachines/jdk1.8.0_172.jdk/Contents/Home/bin/java -Xdock:name=Gradle -Xdock:icon=/Users/cengfanwei/zengfw/ATrain/media/gradle.icns -Dorg.gradle.appname=gradlew -classpath /Users/cengfanwei/zengfw/ATrain/gradle/wrapper/gradle-wrapper.jar org.gradle.wrapper.GradleWrapperMain -v

从打印结果可知，最终其实是通过java命令执行gradle-wrapper.jar包的GradleWrapperMain类，再继续看看GradleWrapperMain干了什么事情...

public class GradleWrapperMain {
    public static final String GRADLE_USER_HOME_OPTION = "g";
    public static final String GRADLE_USER_HOME_DETAILED_OPTION = "gradle-user-home";
    public static final String GRADLE_QUIET_OPTION = "q";
    public static final String GRADLE_QUIET_DETAILED_OPTION = "quiet";

    public static void main(String[] args)
            throws Exception {
        File wrapperJar = wrapperJar();
        File propertiesFile = wrapperProperties(wrapperJar);
        File rootDir = rootDir(wrapperJar);

        CommandLineParser parser = new CommandLineParser();
        parser.allowUnknownOptions();
        parser.option(new String[]{"g", "gradle-user-home"}).hasArgument();
        parser.option(new String[]{"q", "quiet"});

        SystemPropertiesCommandLineConverter converter = new SystemPropertiesCommandLineConverter();
        converter.configure(parser);

        ParsedCommandLine options = parser.parse(args);

        Properties systemProperties = System.getProperties();
        systemProperties.putAll(converter.convert(options, new HashMap()));

        File gradleUserHome = gradleUserHome(options);

        addSystemProperties(gradleUserHome, rootDir);

        Logger logger = logger(options);

        WrapperExecutor wrapperExecutor = WrapperExecutor.forWrapperPropertiesFile(propertiesFile);
        wrapperExecutor.execute(args, new Install(logger, new Download(logger, "gradlew", wrapperVersion()), new PathAssembler(gradleUserHome)), new BootstrapMainStarter());
    }
    
    // ...
}

public class WrapperExecutor {
    // ...
    public void execute(String[] args, Install install, BootstrapMainStarter bootstrapMainStarter) throws Exception {
        File gradleHome = install.createDist(this.config);
        bootstrapMainStarter.start(args, gradleHome);
    }   
    // ...
}

public class BootstrapMainStarter {
    // ...
    public void start(String[] args, File gradleHome) throws Exception {
        File gradleJar = this.findLauncherJar(gradleHome);
        URLClassLoader contextClassLoader = new URLClassLoader(new URL[]{gradleJar.toURI().toURL()}, ClassLoader.getSystemClassLoader().getParent());
        Thread.currentThread().setContextClassLoader(contextClassLoader);
        Class<?> mainClass = contextClassLoader.loadClass("org.gradle.launcher.GradleMain");
        Method mainMethod = mainClass.getMethod("main", String[].class);
        mainMethod.invoke((Object)null, args);
        if (contextClassLoader instanceof Closeable) {
            contextClassLoader.close();
        }
    }   
    // ...
}

public class GradleMain {
    // ...
    public static void main(String[] args) throws Exception {
        (new ProcessBootstrap()).run("org.gradle.launcher.Main", args);
    }
}

public class Main extends EntryPoint {
    // ...
    public static void main(String[] args) {
        (new Main()).run(args);
    }

    protected void doAction(String[] args, ExecutionListener listener) {
        this.createActionFactory().convert(Arrays.asList(args)).execute(listener);
    }

    CommandLineActionFactory createActionFactory() {
        return new CommandLineActionFactory();
    }
}

看到这里比较清晰的，WrapperExecutor会先检查是否有配置已下载到本地的gradle路径，没有则先从服务器下载（根据gradle-wrapper.properties文件配置distributionUrl链接），再是根据传进来的命令行参数，用命令行工厂构建不同的命令行action，并通过命令解析器execute对应的命令行action；

Gradle Wrapper工作流程图

Gradle Wrapper工作流程图

思考：如何避免同个项目在其他开发者电脑上运行时，因gradle版本不同而引发各种问题？

可上传wrapper目录，统一gradle-wrapper.properties配置的gradle版本，使得其他开发者也用同个gradle版本构建同个项目。

以上是关于gradlew脚本的了解，那gradle脚本呢？我们直接打开文件对比，就基本可以知道两份脚本之间的主要差异了：

差异一

差异二

差异之所以在classpath，是因为java命令运行jar包里头的文件的话，我们需要通过classpath指定命令运行时查找class文件的路径。

同样，在gradle脚本中添加 echo "$JAVACMD $@" 日志打印，得到如下打印：

echo "$JAVACMD $@"

$ ~/Library/Android/gradle/gradle-4.4/bin/gradle -v
/Library/Java/JavaVirtualMachines/jdk1.8.0_172.jdk/Contents/Home/bin/java -Xdock:name=Gradle -Xdock:icon=/Users/cengfanwei/Library/Android/gradle/gradle-4.4/media/gradle.icns -Dorg.gradle.appname=gradle -classpath /Users/cengfanwei/Library/Android/gradle/gradle-4.4/lib/gradle-launcher-4.4.jar org.gradle.launcher.GradleMain -v

你会发现如果直接通过gradle命令的话，其实运行的是gradle-launcher-4.4.jar包里头的org.gradle.launcher.GradleMain类，之后的流程就跟上面从GradleMain开始一样的了！

思考：使用gradle命令效率比使用gradlew效率快的原因？

因为gradlew命令，需要执行一些额外流程，如类加载、反射gradle-launcher-xx.jar包里头的类等等，最后再到org.gradle.launcher.GradleMain类的main函数。

二、gradle常用命令

前面了解gradlew、gradle的区别之后，下面列出一些gradle常用的命令