线程"main“java.lang.NoClassDefFoundError: org/apache/log4j/Layout中的异常

Question

我正在尝试使用ant构建一个应用程序。当我构建时，一切看起来都很好，但是我不断地得到上面的错误，因为我已经尝试过了。

• java -jar dist/pmml_export.jar
• java -cp ".:log4j-1.2.16.jar" -jar dist/pmml_export.jar
• java -cp log4j-1.2.16.jar -jar dist/pmml_export.jar

我加倍检查，看看布局是否在我所引用的jar中，它就在那里。我对ant和log4j都很陌生，所以我可能犯了一个明显的错误，但我只是没看到而已。这是我的build.xml。

<?xml version="1.0"?>
<project name="pmml_export" default="archive">

  <target name="init">
    <mkdir dir="build/classes" />
    <mkdir dir="dist" />
  </target>

  <path id="compile.classpath">
    <fileset dir="build/classes" includes="*.class" />
  </path>

  <property name="ant.dir" value="apache-log4j-1.2.16"/>

  <path id="classpath">
    <fileset dir="${ant.dir}" includes="**/*.jar"/>
  </path>

  <target name="exceptions" depends="init">
    <javac srcdir="src/exceptions" destdir="build/classes" classpathref="compile.classpath"/>
    <echo> Exceptions compiled! </echo>
  </target>

  <target name="symbol-table" depends="exceptions" >
    <javac srcdir="src/translator/symbol_table" destdir="build/classes"   classpathref="compile.classpath"/>
    <echo> Symbol table compiled! </echo>
  </target>

  <target name="parser" depends="symbol-table" >
    <javac srcdir="src/translator/parser" destdir="build/classes" classpathref="compile.classpath"/>
    <echo> Parser compiled! </echo>
  </target>

  <target name="lexer" depends="parser" >
    <javac srcdir="src/translator/lexer" destdir="build/classes"  classpathref="compile.classpath"/>
    <echo> Lexer compiled! </echo>
  </target>

  <target name="translator" depends="lexer" >
    <javac srcdir="src/translator" destdir="build/classes" classpathref="compile.classpath"/>
    <echo> Translator compiled! </echo>
  </target>

  <target name="exporter" depends="translator" >
    <javac srcdir="src/pmml_export" destdir="build/classes" classpathref="compile.classpath" />
    <echo> Exporter compiled! </echo>
  </target>

  <target name="archive" depends="exporter" >
    <property name="manifest.mf" location="dist/manifest.txt" />
    <manifest file="${manifest.mf}" >
      <attribute name="Main-Class" value="pmml_export.PMML_Export"/>
    </manifest>
    <jar destfile="dist/pmml_export.jar" manifest="${manifest.mf}"
  basedir="build/classes" />
  </target>

  <target name="run" depends="archive">
    <java jar="dist/pmml_exporter.jar" fork="true">
      <classpath>
        <path refid="classpath"/>
        <path location="dist/pmml_exporter.jar"/>
      </classpath>
    </java>
  </target>
</project>

Answer 1

使用-jar选项时，-cp和-classpath选项将被忽略。使用-jar选项嵌入类路径的正确方法是在jar的MANIFEST.MF文件中设置一个类路径指令。