Spec file

bbs.spec

Name: bbs
Summary: BBS
Version: 1.0
Release: 1
URL: example.com
Source: %{name}-%{version}-%{release}.tar.gz
License: MIT
Group: Applications/Internet
BuildArch: noarch
Requires: java-1.7.0-openjdk, java-1.7.0-openjdk-devel

%description
This is a RPM for bbs project.

%prep
%setup -q

%install
install -d $RPM_BUILD_ROOT/opt/apps
install -p $RPM_BUILD_DIR/%{name}-%{version}/%{name}.war $RPM_BUILD_ROOT/opt/apps/%{name}.war

%post
if [ -d "/usr/local/apache-tomcat-7.0.61/webapps" ]; then
  mv /opt/apps/%{name}.war /usr/local/apache-tomcat-7.0.61/webapps
else
  echo 'please install apache tomcat'
fi

%preun
rm -rf /usr/local/apache-tomcat-7.0.61/webapps/bbs

%postun
service tomcat restart

%files
%attr(644,root,root) /opt/apps/%{name}.war

%clean
rm -rf $RPM_BUILD_ROOT

%changelog
* Wed Apr 22 2015 Zhang Jinwen <jwzhang@thoughtworks.com>
- Build for CentOS-6.4

Several comments:

1. You can add tomcat as a "Requires"
2. If OS does not have tomcat installed, there will be an error calling 'service tomcat restart' in %postun
3. Why don't you restart tomcat after installing this rpm?
4. Another thing is, you cannot write a specific version of tomcat in SPEC
5. in %preun, you don't do any check....