CS520 Web Programming Bits and Pieces of Web Programming (I) Chengyu Sun California State University, Los Angeles

Roadmap Logging Testing View Template Framework Exception Handling

Logging Use print statements to assist debugging Why do we want to do that when we have GUI debugger?? public void foo() { System.out.println( “loop started” ); // some code that might get into infinite loop … System.out.println( “loop finished” ); }

Requirements of Good Logging Tools Minimize performance penalty Support different log output Console, file, database, … Support different message levels Fatal, error, warn, info, debug, trace Easy configuration

Java Logging Libraries Logging implementations Log4j - java.util.logging in JDK Logging API Apache Commons Logging (JCL) Simple Logging Façade for Java (SLF4J) -

Choose Your Logging Libraries Log4j Widely used Good performance Easy configuration java.util.logging Part of JDK, i.e. no extra library dependency Commons Logging Determines logging implementation at runtime SLF4j Statically linked to a logging implementation  Cleaner design  Better performance  Less problem

Using Log4j and SLF4j Library dependencies Coding Creating a Logger Logging statements Configuration Output format

Log4j Configuration File log4j.xml or log4j.properties Appender Output type Output format Logger Package or class selection Message level

Log4j PatternLayout docs/org/apache/log4j/PatternLayout.ht ml

Logging in CSNS2 src/main/resources/log4j.xml build.properties app.log.dir app.log.level Use of Log Viewer plugin in Eclipse

Java Testing Frameworks JUnit Widely used and supported TestNG Technically superior to JUnit (for a while) but not as widely used or supported

What We Want From a Testing Framework Automation Including setup and tear-down Grouping and selection Test Dependency Skip tests that depend on tests that already failed Run independent test in parallel Report Other, e.g. tool support, API, dependency injection, and so on

Maven Support for JUnit/TestNG Library dependency Directory structure src/test/java src/test/resources The surefire plugin

Basic TestNG Method Class Annotations for various before/after methods

Group and groups dependsOnMethods dependsOnGroups

Test Suite A test suite is represented by an XML file and contains one or more tests. Select tests by method, class, package, and group Include and exclude

Test Suite Example testng.xml

TestNG in CSNS2 Configuration Test classes inherit from Spring TestNG support BeforeSuite and AfterSuite methods

More About TestNG TestNG Documenation – main.html main.html Next Generation Java Testing by Cédric Beust and Hani Suleiman

Apache Tiles A template framework for JSP Similar to Master Page and Razor in ASP.NET

The Need for View Templates Header Footer Content 1 Header Footer Content N page1.jsppageN.jsp

Why JSP Is Not Enough It breaks HTML syntax, e.g. in header.jsp and in footer.jsp. It’s difficult to create and manage multiple complex templates.

Basic Tiles Usage Template page = JSP + placeholders (i.e. attributes), Content: JSP, string, other tiles Definition: combine template and content Tiles Tag Library

A Tiles Example Header Footer Content 1 Header Footer Content 2 page1.jsppage2.jsp

Tiles – Template Page Header Footer template.jsp

Tiles – Content Pages Content 1Content 2 page1.jsppage2.jsp

Tiles – Definitions

Resolve Tiles Views in Spring /WEB-INF/tiles.xml

Tiles Usage in CSNS2 WEB-INF/layout for template and header/footer pages WEB-INF/content for content pages WEB-INF/tiles.xml for definitions

Problem with Java Exceptions Too many checked exceptions Checked vs. Runtime exceptions Require lots of boilerplate exception handling code

Spring’s Solution to the Exception Problem Use primarily runtime exceptions Separate exception handling code into exception handlers

Controller Exception Handing in Spring An Exception Resolver handles all runtime exceptions thrown by controllers SimpleMappingExceptionResolverSimpleMappingExceptionResolver maps different exceptions to different views

ExceptionResolver in CSNS2 <bean id="exceptionResolver“ class="csns.web.resolver.ExceptionResolver"> exception/access exception/mail A SimpleMappingExceptionResolver with additional loggin.