Spring MVC – 15 – Exception Handling – 01 | SimpleMappingExceptionResolver
Merhaba Arkadaslar
Bu bolumde Exception Handling konusunu inceleyecegiz. Gercek uygulamalari dusundugumuzde mutlaka beklenmedik hatalara (exception/error) karsi son kullaniciya(end user) uygun bir hata aciklamasi gostermemiz gerekir.
Spring MVC de Exception Handling kavramini XML veya Annotation ile uygulayabiliriz.
Bunun icin kullanacagimiz sinif ve annotationlar ;
- SimpleMappingExceptionResolver
- @ExceptionHandler
- @ResponseStatus
- @ControllerAdvice
Spring MVC & SimpleMappingExceptionResolver
Bu bolumde XML konfigurasyonu ile Exception Handling uygulamasini gelistirelim. SimpleMappingExceptionResolver icin bean tanimini gerceklestirelim ;
14.exception.handling.xmlBased.xml
exceptionMapping icin duzenlemeleri yapalim ;
private Properties exceptionMappings;
java.lang.NumberFormatException firlatildiginda numberFormat.jsp sayfasi
java.lang.NullPointerException firlatildiginda npe.jsp sayfasi
_14.exception.handling.xmlBased.model.DatabaseException firlatildiginda dbException.jsp sayfasi exception handling icin kullanilacak.
... <bean class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver"> <property name="exceptionMappings"> <props> <prop key="java.lang.NumberFormatException">14.exception.handling.xmlBased.view/numberFormat</prop> <prop key="java.lang.NullPointerException">14.exception.handling.xmlBased.view/npe</prop> <prop key="_14.exception.handling.xmlBased.model.DatabaseException"> 14.exception.handling.xmlBased.view/dbException </prop> </props> </property> </bean> ...
SimpleMappingExceptionResolverController.java
Test amacli Controller sinifimizda ilgili exceptionlari firlatacak (throw) sekilde metotlar yazalim.
Dikkat edecek olursak test amacli XML dosyamizda (14.exception.handling.xmlBased.xml) tanimladigimiz NumberFormatException , NullPointerException ve DatabaseException firlatan 3 tane metot tanimladik.
Not : Tabi @Controller ve @RequestMapping icin gerekli XML konfigurasyonu , package tanimlarini unutmayalim.
package _14.exception.handling.xmlBased.controller;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;
import _14.exception.handling.xmlBased.model.DatabaseException;
@Controller
public class SimpleMappingExceptionResolverController {
@RequestMapping("/numberFormatException")
//http://localhost:8080/injavawetrust.springmvc/numberFormatException
public ModelAndView throwNumberFormatException() {
throw new NumberFormatException();
}
@RequestMapping("/nullPointerException")
//http://localhost:8080/injavawetrust.springmvc/nullPointerException
public ModelAndView throwNullPointerException() {
throw new NullPointerException();
}
@RequestMapping("/databaseException")
//http://localhost:8080/injavawetrust.springmvc/databaseException
String throwDatabaseException() throws Exception {
throw new DatabaseException("DB-1000", "DB Connection timeout...");
}
}
DatabaseException.java
package _14.exception.handling.xmlBased.model;
public class DatabaseException extends RuntimeException {
private static final long serialVersionUID = 1L;
private String errCode;
private String errMsg;
//getters and setters
public DatabaseException(String errCode, String errMsg) {
this.errCode = errCode;
this.errMsg = errMsg;
}
}
JSP sayfalarimiz test amacli olacak ve basit olarak ;
NOT : exception JSP implicit objedir.
Servlet & JSP – 18 – Implicit Object & JSP Lifecycle
numberFormat.jsp
<html>
<body>
<h2>numberFormat.jsp</h2>
<h2>${exception}</h2>
</body>
</html>
npe.jsp
<html>
<body>
<h2>npe.jsp</h2>
<h2>${exception}</h2>
</body>
</html>
dbException.jsp
<html>
<body>
<h2>dbException.jsp</h2>
<h2>${exception.errCode}</h2>
<h2>${exception.errMsg}</h2>
</body>
</html>
web.xml
Konfigurasyon dosyasi olarak /WEB-INF/14.exception.handling.xmlBased.xml dosyamizi aktif edelim;
<servlet>
<servlet-name>dispatcher</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet
</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>
<!--
/WEB-INF/01.appContext.xml
/WEB-INF/02.00.appContext.xml
/WEB-INF/03.multiActionController.xml
....
-->
/WEB-INF/14.exception.handling.xmlBased.xml
</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
Uygulamamizi deploy edelim , test etmek icin ;
http://localhost:8080/injavawetrust.springmvc/numberFormatException
http://localhost:8080/injavawetrust.springmvc/nullPointerException
http://localhost:8080/injavawetrust.springmvc/databaseException
Test sonuclarini inceledigimizde , Controller sinifimizda tanimladigimiz ilgili metotlar tarafindan istekler karsilanacaktir. Bu metotlarda throw anahtar kelimesiyle exception firlatiyoruz , (tabi gercek uygulamalarda bu durum beklenmedik hata oldugunda kullaniciya anlamli bir hata mesaji cikartmak icin kullanilacaktir ) , firlatilan hatalara gore npe.jsp , numberFormat.jsp ve dbException.jsp sayfasi gosterilmektedir.
Github kaynak kodlar / source folder
Injavawetrust-springmvc-tutorial
Yazimi burada sonlandiriyorum.
Herkese Bol Javali Gunler dilerim.
Be an oracle man , import java.*;
Levent Erguder
OCP, Java SE 6 Programmer
OCE, Java EE 6 Web Component Developer
Leave a Reply