In the bean validation API javadoc, for every constraint annotation, there's a corresponding .List annotation. For example, for @NotNull , there's @NotNull.List , for which JavaDoc says: Defines several @NotNull annotations on the same element What would you accomplish with multiple @NotNull annotations that you cannot accomplish with one @NotNull ? This is a test to reveal some of the facts. Change the Person class to: package com.example; public class Person { ... Add another JUnit test ( src/test/com/example/TestPersonWithList.java ): package com.example; import java.util.Itera... As the test shows, a Person bean can never be valid because we are requiring that name must begin with Mr and Ms . One might think that the same can be accomplished by simply repeating the @Pattern annotation multiple times,...

Validation groups can be used to control which rules validation rules to run. A validation group can be identified by any Java interface (not class!). Multiple validation groups may be specified when validating. In this example, I added a validation group named MyValidationGroup ( src/main/java/com/example/MyValidationGroup.java in Maven project): package com.example; public interface MyVal... and added a @Size rule for a person's name, because my database can only store up to 15 characters for a person's name: package com.example; import javax.validatio... Now validate Person with a JUnit test ( src/test/java/com/example/TestPersonWithGroup.java in Maven project): package com.example; import java.util.Set; ... Test with " mvn clean test ". The rules where groups is not specified, which belong to the javax.validation.groups.Default group, are not executed with these tests.

A bean class may also be defined through composition. The validation rules of referenced beans are not automatically called when a composite bean is validated. You need to use the @Valid annotation to trigger cascade validation. As an example, I create a class named AccountPerson2 , which contains a Person with the addition of an email field ( src/main/java/com/example/AccountPerson2.java in Maven project): package com.example; import javax.validatio... Now validate AccountPerson2 with a JUnit test ( src/test/java/com/example/AccountPerson2Test.java in Maven project): package com.example; import java.util.Set; ... Test with " mvn clean test " and you'll see that the validation rules of the Person class are executed when an AccountPerson2 bean is validated. Without the @Valid annotation, the validation rules of Person will not be called.

When a bean class inherits another class, the validation rules of the parent class is automatically executed when a child class bean is validated. As an example, I create a class named AccountPerson , which inherits the Person class with the addition of an email field ( src/main/java/com/example/AccountPerson.java in Maven project): package com.example; import javax.validatio... Now validate AccountPerson with a JUnit test ( src/test/java/com/example/AccountPersonTest.java in Maven project): package com.example; import java.util.Set; ... Test with " mvn clean test " and you'll see that the validation rules of the Person class are executed when an AccountPerson bean is validated.

In this simple example, I create a simple validating bean and create a JUnit test to test the validation. The bean ( src/main/java/com/example/Person.java ): package com.example; import javax.validatio... The test ( src/test/java/com/example/TestPerson.java ): package com.example; import java.util.Set; ... Run the test: mvn clean test You'll notice that one test passed and the other failed. The tests require that a person must have a name and the name cannot be empty, so @NotNull is not the right rule to use here. To make sure that the name is not empty, we need to use @Pattern . But since a null String matches any pattern, @NotNull is also needed: package com.example; import javax.validatio...

In this example I'll add a parameter to a facelets template. The example contains three tabs, each tab points to a different page. The tab control is shared among all pages, therefore, it is put in the template. Starting from the simple facelet example , make these additions: Create a new template WEB-INF/templates/tabs.xhtml : <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Stric... Add a page for the about tab ( about.xhtml ): <?xml version="1.0" encoding="UTF-8"?> <ui:comp... Add a page for the news tab ( news.xhtml ): <?xml version="1.0" encoding="UTF-8"?> <ui:comp... Add a page for the partner tab ( partner.xhtml ): <?xml version="1.0" encoding="UTF-8"?> <ui:comp... Build and re-deploy the application. Launch the browser and load page http://localhost:8080/facelet-demo/about.jsf . This is a screenshot:

Facelet templates can be nested, for example, a page can use a template which inherits from another template. To demonstrate this, let's start from the simple example and make these additions: Add a place holder for CSS style sheets in WEB-INF/templates/default.xhtml : <h:head> <title>Facelets Template Demo</tit... Add a derivative template ( WEB-INF/templates/default-style.xhtml ) which provides CSS: <?xml version="1.0" encoding="UTF-8"?> <ui:comp... Add a page that uses the styled template ( home-style.xhtml ): <?xml version="1.0" encoding="UTF-8"?> <ui:comp... The only difference between this file and home.xhtml is the template being used. Compare the display of the pages home.xhtml and home-style.xhtml .

I got this error while building an APK: [apply] [apply] UNEXPECTED TOP-LEVEL ERROR... Apparently the dx tool was running out of memory. The dx script (shell or bat) provides options to pass in Java options, but it's a lot easier just to bump up the default in dx : # By default, give dx a max heap size of 1 gig. Th... Here, I changed the default 1024M to 1624M and resolved the problem.

It is OK to remove elements from a list with Iterator , but you get UnsupportedOperationException if the list is created with Arrays.asList : import java.util.*; public class IteratorRe... Prints: ArrayList test: ================ List size: ...

Read the whole contents of a file into a String. It's better to read the whole file as bytes and convert to String than to read the file line by line and concatenate the lines. String getFileContents(String fileName) throws... Using java.nio : import java.io.FileInputStream; import java...