Calculating dependencies... done!

>>> Emerging (1 of 1) dev-java/dom4j-1.6.1-r1 to /
 * dom4j-1.6.1.tar.gz MD5 ;-) ...                                         [ ok ]
 * dom4j-1.6.1.tar.gz RMD160 ;-) ...                                      [ ok ]
 * dom4j-1.6.1.tar.gz SHA1 ;-) ...                                        [ ok ]
 * dom4j-1.6.1.tar.gz SHA256 ;-) ...                                      [ ok ]
 * dom4j-1.6.1.tar.gz size ;-) ...                                        [ ok ]
 * checking ebuild checksums ;-) ...                                      [ ok ]
 * checking auxfile checksums ;-) ...                                     [ ok ]
 * checking miscfile checksums ;-) ...                                    [ ok ]
 * checking dom4j-1.6.1.tar.gz ;-) ...                                    [ ok ]
 * Using: sun-jdk-1.4
>>> Unpacking source...
>>> Unpacking dom4j-1.6.1.tar.gz to /var/tmp/portage/dom4j-1.6.1-r1/work
tar: A lone zero block at 78061
>>> Source unpacked.
Rewriting ./build.xml
>>> Compiling source in /var/tmp/portage/dom4j-1.6.1-r1/work/dom4j-1.6.1 ...
Buildfile: build.xml

BUILD FAILED
java.lang.UnsupportedClassVersionError: org/xml/sax/ext/Attributes2 (Unsupported major.minor version 49.0)
        at java.lang.ClassLoader.defineClass0(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:539)
        at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:123)
        at java.net.URLClassLoader.defineClass(URLClassLoader.java:251)
        at java.net.URLClassLoader.access$100(URLClassLoader.java:55)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:194)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:187)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:289)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:274)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:235)
        at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:302)
        at java.lang.ClassLoader.defineClass0(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:539)
        at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:123)
        at java.net.URLClassLoader.defineClass(URLClassLoader.java:251)
        at java.net.URLClassLoader.access$100(URLClassLoader.java:55)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:194)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:187)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:289)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:274)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:235)
        at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:302)
        at org.apache.xerces.parsers.AbstractSAXParser.<init>(Unknown Source)
        at org.apache.xerces.parsers.SAXParser.<init>(Unknown Source)
        at org.apache.xerces.parsers.SAXParser.<init>(Unknown Source)
        at org.apache.xerces.jaxp.SAXParserImpl$JAXPSAXParser.<init>(Unknown Source)
        at org.apache.xerces.jaxp.SAXParserImpl.<init>(Unknown Source)
        at org.apache.xerces.jaxp.SAXParserFactoryImpl.newSAXParser(Unknown Source)
        at org.apache.tools.ant.util.JAXPUtils.newSAXParser(JAXPUtils.java:205)
        at org.apache.tools.ant.util.JAXPUtils.getNamespaceXMLReader(JAXPUtils.java:163)
        at org.apache.tools.ant.helper.ProjectHelper2.parse(ProjectHelper2.java:193)
        at org.apache.tools.ant.helper.ProjectHelper2.parse(ProjectHelper2.java:140)
        at org.apache.tools.ant.ProjectHelper.configureProject(ProjectHelper.java:91)
        at org.apache.tools.ant.Main.runBuild(Main.java:653)
        at org.apache.tools.ant.Main.startAnt(Main.java:187)
        at org.apache.tools.ant.launch.Launcher.run(Launcher.java:246)
        at org.apache.tools.ant.launch.Launcher.main(Launcher.java:67)

Total time: 0 seconds
java.lang.UnsupportedClassVersionError: org/xml/sax/ext/Attributes2 (Unsupported major.minor version 49.0)
        at java.lang.ClassLoader.defineClass0(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:539)
        at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:123)
        at java.net.URLClassLoader.defineClass(URLClassLoader.java:251)
        at java.net.URLClassLoader.access$100(URLClassLoader.java:55)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:194)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:187)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:289)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:274)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:235)
        at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:302)
        at java.lang.ClassLoader.defineClass0(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:539)
        at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:123)
        at java.net.URLClassLoader.defineClass(URLClassLoader.java:251)
        at java.net.URLClassLoader.access$100(URLClassLoader.java:55)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:194)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:187)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:289)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:274)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:235)
        at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:302)
        at org.apache.xerces.parsers.AbstractSAXParser.<init>(Unknown Source)
        at org.apache.xerces.parsers.SAXParser.<init>(Unknown Source)
        at org.apache.xerces.parsers.SAXParser.<init>(Unknown Source)
        at org.apache.xerces.jaxp.SAXParserImpl$JAXPSAXParser.<init>(Unknown Source)
        at org.apache.xerces.jaxp.SAXParserImpl.<init>(Unknown Source)
        at org.apache.xerces.jaxp.SAXParserFactoryImpl.newSAXParser(Unknown Source)
        at org.apache.tools.ant.util.JAXPUtils.newSAXParser(JAXPUtils.java:205)
        at org.apache.tools.ant.util.JAXPUtils.getNamespaceXMLReader(JAXPUtils.java:163)
        at org.apache.tools.ant.helper.ProjectHelper2.parse(ProjectHelper2.java:193)
        at org.apache.tools.ant.helper.ProjectHelper2.parse(ProjectHelper2.java:140)
        at org.apache.tools.ant.ProjectHelper.configureProject(ProjectHelper.java:91)
        at org.apache.tools.ant.Main.runBuild(Main.java:653)
        at org.apache.tools.ant.Main.startAnt(Main.java:187)
        at org.apache.tools.ant.launch.Launcher.run(Launcher.java:246)
        at org.apache.tools.ant.launch.Launcher.main(Launcher.java:67)
org/xml/sax/ext/Attributes2 (Unsupported major.minor version 49.0)

!!! ERROR: dev-java/dom4j-1.6.1-r1 failed.
Call stack:
  ebuild.sh, line 1543:   Called dyn_compile
  ebuild.sh, line 938:   Called src_compile
  dom4j-1.6.1-r1.ebuild, line 68:   Called eant 'clean' 'package'
  java-utils-2.eclass, line 1309:   Called die

!!! eant failed
!!! If you need support, post the topmost build error, and the call stack if relevant.

!!! When you file a bug report, please include the following information:
GENTOO_VM=sun-jdk-1.4  CLASSPATH="" JAVA_HOME="/opt/sun-jdk-1.4.2.12"
JAVACFLAGS="-source 1.3 -target 1.3" COMPILER="javac"
and of course, the output of emerge --info