Maven項目中突然找不到Build Path或maven dependencies library

　　這兩天發現有個maven項目抽風了，一個是右擊項目找不到Build Path了，一個是依賴的lib庫沒了，maven引入的依賴包導不了。后來發現是eclipse搞的鬼，出問題的是項目下的.classpath文件變動了。第一個問題是.classpath沒了，而.project文件被改動了；第二個問題這個文件.classpath被改動了。

　　先看這兩個文件被改動后的樣子：

.project

<?xml version="1.0" encoding="UTF-8"?>
<projectDescription>
    <name>ms-navigation-api</name>
    <comment></comment>
    <projects>
    </projects>
    <buildSpec>
        <buildCommand>
            <name>org.eclipse.m2e.core.maven2Builder</name>
            <arguments>
            </arguments>
        </buildCommand>
    </buildSpec>
    <natures>
        <nature>org.eclipse.m2e.core.maven2Nature</nature>
    </natures>
</projectDescription>

.classpath

<?xml version="1.0" encoding="UTF-8"?>
<classpath>
    <classpathentry kind="src" output="target/classes" path="src/main/resources"/>
    <classpathentry kind="src" output="target/classes" path="src/test/java"/>
    <classpathentry kind="src" output="target/classes" path="src/main/java"/>
    <classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/jdk1.8.0_131"/>
    <classpathentry kind="output" path="target/classes"/>
</classpath>

　　

　　改動前的樣子

.project

<?xml version="1.0" encoding="UTF-8"?>
<projectDescription>
    <name>ms-navigation-api</name>
    <comment></comment>
    <projects>
    </projects>
    <buildSpec>
        <buildCommand>
            <name>org.eclipse.jdt.core.javabuilder</name>
            <arguments>
            </arguments>
        </buildCommand>
        <buildCommand>
            <name>org.eclipse.wst.common.project.facet.core.builder</name>
            <arguments>
            </arguments>
        </buildCommand>
        <buildCommand>
            <name>org.eclipse.m2e.core.maven2Builder</name>
            <arguments>
            </arguments>
        </buildCommand>
        <buildCommand>
            <name>org.eclipse.wst.validation.validationbuilder</name>
            <arguments>
            </arguments>
        </buildCommand>
    </buildSpec>
    <natures>
        <nature>org.eclipse.jem.workbench.JavaEMFNature</nature>
        <nature>org.eclipse.wst.common.modulecore.ModuleCoreNature</nature>
        <nature>org.eclipse.jdt.core.javanature</nature>
        <nature>org.eclipse.m2e.core.maven2Nature</nature>
        <nature>org.eclipse.wst.common.project.facet.core.nature</nature>
        <nature>org.eclipse.wst.jsdt.core.jsNature</nature>
    </natures>
</projectDescription>

.classpath　

<?xml version="1.0" encoding="UTF-8"?>
<classpath>
    <classpathentry kind="src" output="target/classes" path="src/main/java">
        <attributes>
            <attribute name="optional" value="true"/>
            <attribute name="maven.pomderived" value="true"/>
        </attributes>
    </classpathentry>
    <classpathentry excluding="**" kind="src" output="target/classes" path="src/main/resources">
        <attributes>
            <attribute name="maven.pomderived" value="true"/>
        </attributes>
    </classpathentry>
    <classpathentry kind="src" output="target/test-classes" path="src/test/java">
        <attributes>
            <attribute name="optional" value="true"/>
            <attribute name="maven.pomderived" value="true"/>
        </attributes>
    </classpathentry>
    <classpathentry kind="src" path="src/test/resources"/>
    <classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.8">
        <attributes>
            <attribute name="maven.pomderived" value="true"/>
        </attributes>
    </classpathentry>
    <classpathentry kind="con" path="org.eclipse.m2e.MAVEN2_CLASSPATH_CONTAINER">
        <attributes>
            <attribute name="maven.pomderived" value="true"/>
            <attribute name="org.eclipse.jst.component.dependency" value="/WEB-INF/lib"/>
        </attributes>
    </classpathentry>
    <classpathentry kind="output" path="target/classes"/>
</classpath>

　　

　　各個maven項目.classpath文件都是一樣的，所以這兩個問題都需要找到另一個.classpath文件，復制到有問題的項目，而第二個問題還要做一件事：參考另一個.project文件，把缺失的內容補上（內容都是一樣的，除了項目名）。改好后重啟Eclipse，Build Path和Maven Dependecies終於又回來了。