Set and check for Java version 1.7.

build.properties.template

@@ -1,3 +1,5 @@
 # This file is part of Kitodo.ContentServer
 
+#java.source=1.7
+#java.target=1.7
 tomcat.dir.lib=/usr/share/tomcat7/lib

build.xml

@@ -8,6 +8,9 @@
 
     <property name="build.dir" value="build" />
 
+    <property name="build.javac.target" value="1.7"/>
+    <property name="build.javac.source" value="1.7"/>
+
     <property name="build.dist.name" value="ics" />
     <property name="build.dist.version" value="1.1.5" />
 
@@ -41,7 +44,24 @@
         </condition>
     </target>
 
-    <target name="checkConditions" depends="checkServletApi" />
+    <target name="checkConditions" depends="checkJavaVersion, checkServletApi" />
+
+    <!-- check for Java version 1.7 -->
+    <target name="checkJavaVersion">
+        <fail message="Build required at least version 1.7 of the Java compiler ">
+            <condition>
+                <and>
+                    <contains string="${java.version}" substring="1.0"/>
+                    <contains string="${java.version}" substring="1.1"/>
+                    <contains string="${java.version}" substring="1.2"/>
+                    <contains string="${java.version}" substring="1.3"/>
+                    <contains string="${java.version}" substring="1.4"/>
+                    <contains string="${java.version}" substring="1.5"/>
+                    <contains string="${java.version}" substring="1.6"/>
+                </and>
+            </condition>
+        </fail>
+    </target>
 
     <target name="checkServletApi" depends="checkServletClassPath" unless="servletapi.present">
         <echo>Servlet API not found on classpath!</echo>
@@ -67,6 +87,8 @@
         <echo>compile sources</echo>
         <javac destdir="build"
             includeAntRuntime="false"
+            source="${build.javac.source}"
+            target="${build.javac.target}"
             encoding="UTF-8"
             debug="true"
             debuglevel="lines,vars,source"