change version java runtime in tomcat7

Tomcat dont execute default version java in linux machine. to view what version java use proccess tomcat type this

#ps -ef | grep tomcat

tomcat7  13692     1  1 10:57 ?        00:00:07 /usr/lib/jvm/default-java/bin/java -Djava.util.logging.config.file=/var/lib/tomcat7/conf/logging.properties -Djava.awt.headless=true -Xmx128m -XX:+UseConcMarkSweepGC -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djava.endorsed.dirs=/usr/share/tomcat7/endorsed -classpath /usr/share/tomcat7/bin/bootstrap.jar:/usr/share/tomcat7/bin/tomcat-juli.jar -Dcatalina.base=/var/lib/tomcat7 -Dcatalina.home=/usr/share/tomcat7 -Djava.io.tmpdir=/tmp/tomcat7-tomcat7-tmp org.apache.catalina.startup.Bootstrap start

To view default java version

#java -version 

java version "1.7.0_21"
Java(TM) SE Runtime Environment (build 1.7.0_21-b11)
Java HotSpot(TM) 64-Bit Server VM (build 23.21-b01, mixed mode)

and execute default java

#/usr/lib/jvm/default-java/bin/java -version


java version "1.6.0_27"
OpenJDK Runtime Environment (IcedTea6 1.12.5) (6b27-1.12.5-0ubuntu0.12.04.1)
OpenJDK 64-Bit Server VM (build 20.0-b12, mixed mode)

#update-java-alternatives  -l

j2sdk1.6-oracle 315 /usr/lib/jvm/j2sdk1.6-oracle
java-1.6.0-openjdk-amd64 1061 /usr/lib/jvm/java-1.6.0-openjdk-amd64
java-1.7.0-openjdk-amd64 1051 /usr/lib/jvm/java-1.7.0-openjdk-amd64
java-7-oracle 1062 /usr/lib/jvm/java-7-oracle

show soft link to java 1.6

#/usr/lib/jvm/ ls -la 
default-java -> java-1.6.0-openjdk-amd64

remove soft link to 1.6 and create a new link 1.7

# unlink default-java
# ln -f  -s java-7-oracle /usr/lib/jvm/default-java

show new link to 1.7

#/usr/lib/jvm/ ls -la 
default-java -> java-7-oracle