Maven

Manage additional JAR files and supporting dependencies and build paths issues.. pom.xml+src(main、test)+target 这样子的文件结构是 maven 特有的

Scope

• compile: 编译时需要用到该jar包（默认）如 commons-logging。
• test: 编译 test 时用到，如 junit。
• provided: 编译时需要用到，但运行时由JDK或某个服务器提供。
  • 如 servelt-api.（比如中天老项目里，就要额外加载下 tomcat 的 lib）
• runtime: 编译时不需要，但运行时需要用到，如 mysql
  • 典型使用场景：jdbc-drivers. 最大的目的是为了 dynamic-loading. the classes within the library are present to the JVM classpath (runtime environment), but not to the Java compiler classpath (compile-time), therefore when compiling your project these classes will not be visible to the compiler.. therefore you cannot use/import any of these classes at compile-time. refs: java - When would I need maven dependency with runtime scope - Stack Overflow (想到前端其实就一个 --save 和 --save-dev，基本上 dev 都只与本地开发相关，因为不用怎么依赖容器)

pom file

• project meta data: groupId(reversed domain name) + artifactId(project name) + versionId = GAV
• dependencies
• Spring Boot Starters: A collection of Maven dependencies
• plug ins (additional tasks)
• Spring boot maven plugin

构建流程

使用 Maven 构建项目就是执行 lifecycle，执行到指定的 phase 为止。每个 phase 会执行自己默认的一个或多个 goal。goal 是最小任务单元。

如 mvn compile ，Maven 将执行到compile这个 phase，这个 phase 会调用 compiler 插件执行关联的 compiler:compile 这个goal。这些都是内置在 maven 里的标准插件。

实际上，执行每个phase，都是通过某个插件（plugin）来执行的，Maven本身其实并不知道如何执行compile，它只是负责找到对应的compiler插件，然后执行默认的compiler:compile这个goal来完成编译

引入自定义插件就也需要指定 phase 和 goal.

多模块

-pl + 模块名 / --projects ：That's why you should always build a sub-module from its aggregator/parent and via the -pl and -am options, to make sure that:

Maven wrapper files

• 相当于嵌在项目里的 nvm ！给一个项目提供一个独立的，指定版本的Maven给它使用。
• 在项目下执行 mvn wrapper:wrapper -Dmaven=3.9.0 可以生成
• mvnw 注释

#!/bin/sh
# ----------------------------------------------------------------------------

# ----------------------------------------------------------------------------
# Maven Start Up Batch script
#
# Required ENV vars:
# ------------------
#   JAVA_HOME - location of a JDK home dir
#
# Optional ENV vars
# -----------------
#   M2_HOME - location of maven2's installed home dir
#   MAVEN_OPTS - parameters passed to the Java VM when running Maven
#     e.g. to debug Maven itself, use
#       set MAVEN_OPTS=-Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=8000
#   MAVEN_SKIP_RC - flag to disable loading of mavenrc files
# ----------------------------------------------------------------------------

if [ -z "$MAVEN_SKIP_RC" ] ; then

  if [ -f /etc/mavenrc ] ; then
    . /etc/mavenrc
  fi

  if [ -f "$HOME/.mavenrc" ] ; then
    . "$HOME/.mavenrc"
  fi

fi

# OS specific support.  $var _must_ be set to either true or false.
cygwin=false;
darwin=false;
mingw=false
case "`uname`" in
  CYGWIN*) cygwin=true ;;
  MINGW*) mingw=true;;
  Darwin*) darwin=true
    # Use /usr/libexec/java_home if available, otherwise fall back to /Library/Java/Home
    # See https://developer.apple.com/library/mac/qa/qa1170/_index.html
    if [ -z "$JAVA_HOME" ]; then #  is zero length
      if [ -x "/usr/libexec/java_home" ]; then # -x filename 如果 filename可执行，则为真
        export JAVA_HOME="`/usr/libexec/java_home`"
      else
        export JAVA_HOME="/Library/Java/Home"
      fi
    fi
    ;;
esac

if [ -z "$JAVA_HOME" ] ; then
  if [ -r /etc/gentoo-release ] ; then
    JAVA_HOME=`java-config --jre-home`
  fi
fi

if [ -z "$M2_HOME" ] ; then
            echo "不存在 M2_HOME"
  ## resolve links - $0 may be a link to maven's home
  PRG="$0"
   echo "PRG=\$0 $0"

  # need this for relative symlinks
  while [ -h "$PRG" ] ; do # 如果FILE 存在且是一个符号连接则为真
    echo "-h $PRG"
    ls=`ls -ld "$PRG"`
    link=`expr "$ls" : '.*-> \(.*\)$'` # 这个没懂诶
    if expr "$link" : '/.*' > /dev/null; then # /dev/null 是一个空设备文件，它充当一个黑洞，所有写入该设备的数据都会被丢弃，不会在系统中保留或保存。 当程序需要执行某个操作但不希望产生任何输出时，可以将输出重定向到 /dev/null
      PRG="$link"
    else
      PRG="`dirname "$PRG"`/$link"
    fi
  done

   echo "PRG2= $0"

  saveddir=`pwd`

  M2_HOME=`dirname "$PRG"`/..

  echo "M2_HOME $M2_HOME"

  # make it fully qualified
  M2_HOME=`cd "$M2_HOME" && pwd`

  echo "M2_HOME $M2_HOME"

  cd "$saveddir"
  # echo Using m2 at $M2_HOME
fi

# For Cygwin, ensure paths are in UNIX format before anything is touched
if $cygwin ; then
  [ -n "$M2_HOME" ] &&
    M2_HOME=`cygpath --unix "$M2_HOME"`
  [ -n "$JAVA_HOME" ] &&
    JAVA_HOME=`cygpath --unix "$JAVA_HOME"`
  [ -n "$CLASSPATH" ] &&
    CLASSPATH=`cygpath --path --unix "$CLASSPATH"`
fi

# For Mingw, ensure paths are in UNIX format before anything is touched
if $mingw ; then
  [ -n "$M2_HOME" ] &&
    M2_HOME="`(cd "$M2_HOME"; pwd)`"
  [ -n "$JAVA_HOME" ] &&
    JAVA_HOME="`(cd "$JAVA_HOME"; pwd)`"
fi

if [ -z "$JAVA_HOME" ]; then
  javaExecutable="`which javac`"
  if [ -n "$javaExecutable" ] && ! [ "`expr \"$javaExecutable\" : '\([^ ]*\)'`" = "no" ]; then
    # readlink(1) is not available as standard on Solaris 10.
    readLink=`which readlink`
    if [ ! `expr "$readLink" : '\([^ ]*\)'` = "no" ]; then
      if $darwin ; then
        javaHome="`dirname \"$javaExecutable\"`"
        javaExecutable="`cd \"$javaHome\" && pwd -P`/javac"
      else
        javaExecutable="`readlink -f \"$javaExecutable\"`"
      fi
      javaHome="`dirname \"$javaExecutable\"`"
      javaHome=`expr "$javaHome" : '\(.*\)/bin'`
      JAVA_HOME="$javaHome"
      export JAVA_HOME
    fi
  fi
fi

if [ -z "$JAVACMD" ] ; then
  if [ -n "$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
  else
    JAVACMD="`which java`"
  fi
fi

echo "JAVACMD = $JAVACMD"

if [ ! -x "$JAVACMD" ] ; then
  echo "Error: JAVA_HOME is not defined correctly." >&2
  echo "  We cannot execute $JAVACMD" >&2
  exit 1
fi

if [ -z "$JAVA_HOME" ] ; then
  echo "Warning: JAVA_HOME environment variable is not set."
fi

CLASSWORLDS_LAUNCHER=org.codehaus.plexus.classworlds.launcher.Launcher

# traverses directory structure from process work directory to filesystem root
# first directory with .mvn subdirectory is considered project base directory
find_maven_basedir() {

  if [ -z "$1" ]
  then
    echo "Path not specified to find_maven_basedir"
    return 1
  fi

  basedir="$1"
  wdir="$1"
  while [ "$wdir" != '/' ] ; do
    if [ -d "$wdir"/.mvn ] ; then
      basedir=$wdir
      break
    fi
    # workaround for JBEAP-8937 (on Solaris 10/Sparc)
    if [ -d "${wdir}" ]; then
      wdir=`cd "$wdir/.."; pwd`
    fi
    # end of workaround
  done
  echo "${basedir}"
}

# concatenates all lines of a file
concat_lines() {
  if [ -f "$1" ]; then
    echo "$(tr -s '\n' ' ' < "$1")"
  fi
}

BASE_DIR=`find_maven_basedir "$(pwd)"`
echo "BASE_DIR = $BASE_DIR"
if [ -z "$BASE_DIR" ]; then
  exit 1;
fi

##########################################################################################
# Extension to allow automatically downloading the maven-wrapper.jar from Maven-central
# This allows using the maven wrapper in projects that prohibit checking in binary data.
##########################################################################################
if [ -r "$BASE_DIR/.mvn/wrapper/maven-wrapper.jar" ]; then # checks if the argument that follows it is a file, it exists, and it's readable
    if [ "$MVNW_VERBOSE" = true ]; then
      echo "Found .mvn/wrapper/maven-wrapper.jar"
    fi
else
    if [ "$MVNW_VERBOSE" = true ]; then
      echo "Couldn't find .mvn/wrapper/maven-wrapper.jar, downloading it ..."
    fi
    if [ -n "$MVNW_REPOURL" ]; then
      jarUrl="$MVNW_REPOURL/io/takari/maven-wrapper/0.5.6/maven-wrapper-0.5.6.jar"
    else
      jarUrl="https://repo.maven.apache.org/maven2/io/takari/maven-wrapper/0.5.6/maven-wrapper-0.5.6.jar"
    fi
    while IFS="=" read key value; do
      case "$key" in (wrapperUrl) jarUrl="$value"; break ;;
      esac
    done < "$BASE_DIR/.mvn/wrapper/maven-wrapper.properties"
    if [ "$MVNW_VERBOSE" = true ]; then
      echo "Downloading from: $jarUrl"
    fi
    wrapperJarPath="$BASE_DIR/.mvn/wrapper/maven-wrapper.jar"
    if $cygwin; then
      wrapperJarPath=`cygpath --path --windows "$wrapperJarPath"`
    fi

    if command -v wget > /dev/null; then
        if [ "$MVNW_VERBOSE" = true ]; then
          echo "Found wget ... using wget"
        fi
        if [ -z "$MVNW_USERNAME" ] || [ -z "$MVNW_PASSWORD" ]; then
            wget "$jarUrl" -O "$wrapperJarPath"
        else
            wget --http-user=$MVNW_USERNAME --http-password=$MVNW_PASSWORD "$jarUrl" -O "$wrapperJarPath"
        fi
    elif command -v curl > /dev/null; then
        if [ "$MVNW_VERBOSE" = true ]; then
          echo "Found curl ... using curl"
        fi
        if [ -z "$MVNW_USERNAME" ] || [ -z "$MVNW_PASSWORD" ]; then
            curl -o "$wrapperJarPath" "$jarUrl" -f
        else
            curl --user $MVNW_USERNAME:$MVNW_PASSWORD -o "$wrapperJarPath" "$jarUrl" -f
        fi

    else
        if [ "$MVNW_VERBOSE" = true ]; then
          echo "Falling back to using Java to download"
        fi
        javaClass="$BASE_DIR/.mvn/wrapper/MavenWrapperDownloader.java"
        # For Cygwin, switch paths to Windows format before running javac
        if $cygwin; then
          javaClass=`cygpath --path --windows "$javaClass"`
        fi
        if [ -e "$javaClass" ]; then
            if [ ! -e "$BASE_DIR/.mvn/wrapper/MavenWrapperDownloader.class" ]; then
                if [ "$MVNW_VERBOSE" = true ]; then
                  echo " - Compiling MavenWrapperDownloader.java ..."
                fi
                # Compiling the Java class
                ("$JAVA_HOME/bin/javac" "$javaClass")
            fi
            if [ -e "$BASE_DIR/.mvn/wrapper/MavenWrapperDownloader.class" ]; then
                # Running the downloader
                if [ "$MVNW_VERBOSE" = true ]; then
                  echo " - Running MavenWrapperDownloader.java ..."
                fi
                ("$JAVA_HOME/bin/java" -cp .mvn/wrapper MavenWrapperDownloader "$MAVEN_PROJECTBASEDIR")
            fi
        fi
    fi
fi
##########################################################################################
# End of extension
##########################################################################################

export MAVEN_PROJECTBASEDIR=${MAVEN_BASEDIR:-"$BASE_DIR"}
if [ "$MVNW_VERBOSE" = true ]; then
  echo $MAVEN_PROJECTBASEDIR
fi
MAVEN_OPTS="$(concat_lines "$MAVEN_PROJECTBASEDIR/.mvn/jvm.config") $MAVEN_OPTS"

echo "MAVEN_OPTS = ${MAVEN_OPTS}"

# For Cygwin, switch paths to Windows format before running java
if $cygwin; then
  [ -n "$M2_HOME" ] &&
    M2_HOME=`cygpath --path --windows "$M2_HOME"`
  [ -n "$JAVA_HOME" ] &&
    JAVA_HOME=`cygpath --path --windows "$JAVA_HOME"`
  [ -n "$CLASSPATH" ] &&
    CLASSPATH=`cygpath --path --windows "$CLASSPATH"`
  [ -n "$MAVEN_PROJECTBASEDIR" ] &&
    MAVEN_PROJECTBASEDIR=`cygpath --path --windows "$MAVEN_PROJECTBASEDIR"`
fi

# Provide a "standardized" way to retrieve the CLI args that will
# work with both Windows and non-Windows executions.
MAVEN_CMD_LINE_ARGS="$MAVEN_CONFIG $@"
export MAVEN_CMD_LINE_ARGS

echo "MAVEN_CMD_LINE_ARGS = ${MAVEN_CMD_LINE_ARGS}"

WRAPPER_LAUNCHER=org.apache.maven.wrapper.MavenWrapperMain

echo "$JAVACMD" \
       $MAVEN_OPTS \
       -classpath "$MAVEN_PROJECTBASEDIR/.mvn/wrapper/maven-wrapper.jar" \
       "-Dmaven.home=${M2_HOME}" "-Dmaven.multiModuleProjectDirectory=${MAVEN_PROJECTBASEDIR}" \
       ${WRAPPER_LAUNCHER} $MAVEN_CONFIG "$@"

exec "$JAVACMD" \
  $MAVEN_OPTS \
  -classpath "$MAVEN_PROJECTBASEDIR/.mvn/wrapper/maven-wrapper.jar" \
  "-Dmaven.home=${M2_HOME}" "-Dmaven.multiModuleProjectDirectory=${MAVEN_PROJECTBASEDIR}" \
  ${WRAPPER_LAUNCHER} $MAVEN_CONFIG "$@"

Pass JVM arguments

How to Pass JVM Arguments via Maven | Baeldung

发布 Artifact

<distributionManagement>  
    <repository>  
        <!-- 注意这里的 id 要与 ~/.m2/settings.xml 里配置的 id 一致 -->
        <id>byteox-official</id>
        <name>User Porject Release</name>  
        <url>${distribution.repo.url}</url>  
    </repository>  
</distributionManagement>

pom.xml v.s. setting.xml

• settings.xml is your user preferences. It lives in your main Maven directory (usually $HOME/.m2) and holds your own settings, like listings for non-public repositories, usernames, and other personalized configuration.
• pom.xml is the control file for each Maven project or module.