Spring AOP with annotation

Aspect

Combination of advice and pointcuts.

Advice

The implementation of functionality that will be applied.

Pointcut

A rule for matching the parts of the object model that the functionality will be applied to.

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Enable annotation

<aop:aspectj-autoproxy />

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Aspect

package org.xyz;
import org.aspectj.lang.annotation.Aspect;

@Aspect
public class NotVeryUsefulAspect {

}

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Pointcut

@Pointcut("execution(* transfer(..))")// the pointcut expression
private void anyOldTransfer() {}// the pointcut signature

Combining pointcut expressions

@Pointcut("execution(public * *(..))")
private void anyPublicOperation() {}
    
@Pointcut("within(com.xyz.someapp.trading..*)")
private void inTrading() {}
    
@Pointcut("anyPublicOperation() && inTrading()")
private void tradingOperation() {}

@Aspect
public class BeforeAspect {
                                                            
  @Pointcut("execution(* com.apress.prospring2.ch06.services.*.*(..))")
  private void serviceExecution() { }
  @Pointcut(
      "execution(* com.apress.prospring2.ch06.services.UserService.login(..))")
  private void loginExecution() { }
  @Before("serviceExecution() && !loginExecution()")
  public void beforeLogin() throws Throwable {
      if (SecurityContext.getCurrentUser() == null)
          throw new RuntimeException("Must login to call this method.");
  }
}

Sharing common pointcut definitions

package com.xyz.someapp;

import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Pointcut;

@Aspect
public class SystemArchitecture {

  /**
   * A join point is in the web layer if the method is defined
   * in a type in the com.xyz.someapp.web package or any sub-package
   * under that.
   */
  @Pointcut("within(com.xyz.someapp.web..*)")
  public void inWebLayer() {}

  /**
   * A join point is in the service layer if the method is defined
   * in a type in the com.xyz.someapp.service package or any sub-package
   * under that.
   */
  @Pointcut("within(com.xyz.someapp.service..*)")
  public void inServiceLayer() {}

  /**
   * A join point is in the data access layer if the method is defined
   * in a type in the com.xyz.someapp.dao package or any sub-package
   * under that.
   */
  @Pointcut("within(com.xyz.someapp.dao..*)")
  public void inDataAccessLayer() {}

  /**
   * A business service is the execution of any method defined on a service
   * interface. This definition assumes that interfaces are placed in the
   * "service" package, and that implementation types are in sub-packages.
   * 
   * If you group service interfaces by functional area (for example, 
   * in packages com.xyz.someapp.abc.service and com.xyz.def.service) then
   * the pointcut expression "execution(* com.xyz.someapp..service.*.*(..))"
   * could be used instead.
   *
   * Alternatively, you can write the expression using the 'bean'
   * PCD, like so "bean(*Service)". (This assumes that you have
   * named your Spring service beans in a consistent fashion.)
   */
  @Pointcut("execution(* com.xyz.someapp.service.*.*(..))")
  public void businessService() {}
  
  /**
   * A data access operation is the execution of any method defined on a 
   * dao interface. This definition assumes that interfaces are placed in the
   * "dao" package, and that implementation types are in sub-packages.
   */
  @Pointcut("execution(* com.xyz.someapp.dao.*.*(..))")
  public void dataAccessOperation() {}

}

Examples of common pointcut expressions

execution(public * *(..))

the execution of any public method

execution(* set*(..))

the execution of any method with a name beginning with "set"

execution(* com.xyz.service.AccountService.*(..))

the execution of any method defined by the AccountService interface

execution(* com.xyz.service.*.*(..))

he execution of any method defined in the service package

execution(* com.xyz.service..*.*(..))

the execution of any method defined in the service package or a sub-package

within(com.xyz.service.*)

any join point (method execution only in Spring AOP) within the service package

within(com.xyz.service.*)

any join point (method execution only in Spring AOP) within the service package

within(com.xyz.service..*)

any join point (method execution only in Spring AOP) within the service package or a sub-package

this(com.xyz.service.AccountService)

any join point (method execution only in Spring AOP) where the proxy implements the AccountService interface

target(com.xyz.service.AccountService)

any join point (method execution only in Spring AOP) where the target object implements the AccountService interface

args(java.io.Serializable)

any join point (method execution only in Spring AOP) which takes a single parameter, and where the argument passed at runtime is Serializable

@target(org.springframework.transaction.annotation.Transactional)

any join point (method execution only in Spring AOP) where the target object has an @Transactional annotation

@annotation(org.springframework.transaction.annotation.Transactional)

any join point (method execution only in Spring AOP) where the executing method has an @Transactional annotation

@args(com.xyz.security.Classified)

any join point (method execution only in Spring AOP) which takes a single parameter, and where the runtime type of the argument passed has the @Classified annotation

bean(tradeService

any join point (method execution only in Spring AOP) on a Spring bean named 'tradeService'

bean(*Service)

any join point (method execution only in Spring AOP) on Spring beans having names that match the wildcard expression '*Service'

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Advice

As parameter of advice method you can use org.aspectj.lang.JoinPoint. Class which implements this interface have method: getTarget(), getArgs(), getSignature(), getThis(). You can use this method in advice. For example see @After advice.

Advice with reference to pointcut

import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;

@Aspect
public class BeforeExample {

  @Before("com.xyz.myapp.SystemArchitecture.dataAccessOperation()")
  public void doAccessCheck() {
    // ...
  }

}

Advice with in-place pointcut

import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;

@Aspect
public class BeforeExample {

  @Before("execution(* com.xyz.myapp.dao.*.*(..))")
  public void doAccessCheck() {
    // ...
  }

}

After returning advice

import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.AfterReturning;

@Aspect
public class AfterReturningExample {

  @AfterReturning(
    pointcut="com.xyz.myapp.SystemArchitecture.dataAccessOperation()",
    returning="retVal")
  public void doAccessCheck(Object retVal) {
    // ...
  }
  
}

After throwing advice

import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.AfterThrowing;

@Aspect
public class AfterThrowingExample {

  @AfterThrowing(
    pointcut="com.xyz.myapp.SystemArchitecture.dataAccessOperation()",
    throwing="ex")
  public void doRecoveryActions(DataAccessException ex) {
    // ...
  }

}

After (finally) advice

import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.After;

@Aspect
public class AfterFinallyExample {

  @After("com.xyz.myapp.SystemArchitecture.dataAccessOperation()")
  public void doReleaseLock( JoinPoint jp ) {
    // ...
    Object[] targetMethodArgs = jp.getArgs();
    //...
  }

}

Around advice

import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.ProceedingJoinPoint;

@Aspect
public class AroundExample {

  @Around("com.xyz.myapp.SystemArchitecture.businessService()")
  public Object doBasicProfiling(ProceedingJoinPoint pjp) throws Throwable {
    // start stopwatch
    Object retVal = pjp.proceed();
    // stop stopwatch
    return retVal;
  }

}

Passing parameters to advice

@Before("com.xyz.myapp.SystemArchitecture.dataAccessOperation() &&" + 
        "args(account,..)")
public void validateAccount(Account account) {
  // ...
}

@Pointcut("com.xyz.myapp.SystemArchitecture.dataAccessOperation() &&" + 
          "args(account,..)")
private void accountDataAccessOperation(Account account) {}

@Before("accountDataAccessOperation(account)")
public void validateAccount(Account account) {
  // ...
}

@Before(
   value="com.xyz.lib.Pointcuts.anyPublicMethod() && target(bean) && @annotation(auditable)",
   argNames="bean,auditable")
public void audit(JoinPoint jp, Object bean, Auditable auditable) {
  AuditCode code = auditable.value();
  // ... use code, bean, and jp
}

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Exception handling in Spring MVC

SimpleMappingExceptionResolver

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Specific Exception handler

Class SimpleleMappingExceptionResolver implements interface HandlerExceptionResolver. You can implement own specific class or extends class SimpleleMappingExceptionResolver.

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MailErrorHandlerException

If occure some exception it send mail.

public class ErrorHandlerController implements HandlerExceptionResolver{

    public static final String DEFAULT_EXCEPTION_ATTRIBUTE = "exception";
    public static final String DEFAULT_ERROR_WIEW = "error";
   
    private MailManager mailManager;
    private String from;
    private String to;
    private String subject;
    private String defaultErrorView = DEFAULT_ERROR_WIEW;
    private String exceptionAttribute = DEFAULT_EXCEPTION_ATTRIBUTE;

    @Override
    public ModelAndView resolveException(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) {

        if (mailManager != null && from != null && to != null && subject != null){
            sendMailToWebmaster(ex);
        }

        return getModelAndView(defaultErrorView, ex);
    }

    private void sendMailToWebmaster(Exception ex) {
        mailManager.setFrom(  from );
        mailManager.setTo( to );
        mailManager.setSubject( subject );
        mailManager.setText( stack2string( ex ));
        mailManager.sendMail();
    }

    protected ModelAndView getModelAndView(String viewName, Exception ex) {
         ModelAndView mv = new ModelAndView(viewName);       
         mv.addObject(this.exceptionAttribute, ex);      
         return mv;
    }

    public static String stack2string(Exception e) {
            StringWriter sw = new StringWriter();
            PrintWriter pw = new PrintWriter(sw);
            e.printStackTrace(pw);
            return "------\r\n" + sw.toString() + "------\r\n";
    }
    
    public void setDefaultErrorView(String defaultErrorView) {
        this.defaultErrorView = defaultErrorView;
    }

    public void setExceptionAttribute(String exceptionAttribute) {
        this.exceptionAttribute = exceptionAttribute;
    }

    public void setMailManager(MailManager mailManager) {
        this.mailManager = mailManager;
    }

    public void setFrom(String from) {
        this.from = from;
    }

    public void setSubject(String subject) {
        this.subject = subject;
    }

    public void setTo(String to) {
        this.to = to;
    }
}

Tag checkboxes in Spring MVC

In jsp page with Spring MVC you can use form tags.

With tag checkboxes you can create elegant structure of code in form, for example if you have typical 1:N or M:N relation between model classes.

I show 1:N relation between SECTION and PRODUCT class. It example uses Spring MVC and form-tag checkboxes.

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Class Section

Section class is common POJO. Class contains reference to Product class.

public class Section {
    ...
    private List products;
    ...        
}

Class Product

Correct designed method boolean equals:Obj is very important for useful usage checkboxes tag.

public class Product {
    
    private Integer Id;
    private String title;
    
    ...

    @Override
    public boolean equals(Object obj) {
        if (obj == null) {
            return false;
        }
        if (getClass() != obj.getClass()) {
            return false;
        }
        final Product other = (Product) obj;
        if (this.Id != other.Id && (this.Id == null || !this.Id.equals(other.Id))) {
            return false;
        }
        if ((this.title == null) ? (other.title != null) : !this.title.equals(other.title)) {
            return false;
        }
        return true;
    }
}

Controller

It is important create Property editor for reference class (Product). Property editor is register in method initBinder. As you see the attribute allProducts in method getAllProducts is automatically putting to model. It is need in view section_edit.jsp.

@ModelAttribute("allProducts")
public List getAllProducts(){
     return productDao.all();
}

@RequestMapping(value="/section_edit.htm", method=RequestMethod.GET)   
public Section sectionEdit(Integer sectionId){
     return sectionDao.findById(sectionId);
}

@RequestMapping(value="/section_edit.htm", method=RequestMethod.POST)   
public String sectionEdit(Section section, Errors errors){               
     ...
     sectionDao.saveOrUpdate(section);
     return "redirect:/sections.htm";
}

@InitBinder
public void initBinder(WebDataBinder binder) {       
   binder.registerCustomEditor(Product.class, new ProductPropertyEditor());     
}

ProductPropertyEditor

In ProductProperty editor I override only method void setAsText:String. This method create Product instance from product.id represented as test in jsp form (section_edit.jsp).

public class ProductPropertyEditor extends PropertyEditorSupport{
    ...        
    @Override
    public void setAsText(final String text) {
        setValue(productDao.findById(Integer.parseInt(text)));
    }
    
}

section_edit.jsp

Expression ${allProducts} read model attribute allProduct setting in controller. It contain List of all products. As value of checkboxes tag attribute itemValue I set id. It use product.id value and this value can read method void setAsText:String from ProductPropertyEditor, when user submit form.

When tag checkboxes iterate items allProducts, then every Product from allProducts List is compare with Product from Section.products List. When they are the same, then will be rendered checkbox with checked attribute.

Checkbox will bee checked when Product from List of Section.products equals Product from List of allProduct.

You must override toString method in reference object (Product). It is very important behaviour of checkboxes tag from Spring checkboxes tag documentation.

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Conclusion

Checkbox is checked when:

• Property is Collection or array and contains the same Object as wrapped Collection.