Revision: 237ad22b80df
Author: eatnumber1 <[email protected]>
Date: Fri Apr 11 02:12:01 2014 UTC
Log: Created BoundFields page.
http://code.google.com/p/google-guice/source/detail?r=237ad22b80df&repo=wiki
Added:
/BoundFields.wiki
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--- /dev/null
+++ /BoundFields.wiki Fri Apr 11 02:12:01 2014 UTC
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+#summary Automatically bind field's values to their types.
+
+= !BoundFields =
+
+Test code which uses Guice frequently follows the pattern whereby you
create several fields in your test class and bind those fields to their
types using a custom Module. BoundFieldModule can help simplify this
pattern by automatically binding fields annotated with @Bind.
+
+== Binding Fields Manually ==
+Frequently in order to test classes which are injected, you need to inject
mocks or dummy values for the tested class's dependencies. In order to do
this, a common pattern is the following:
+{{{
+public class TestFoo {
+ private Bar barMock;
+
+ // Foo depends on Bar.
+ @Inject private Foo foo;
+
+ @Before public void setUp() {
+ barMock = ...;
+ Guice.createInjector(getTestModule()).injectMembers(this);
+ }
+
+ private Module getTestModule() {
+ return new AbstractModule() {
+ @Override
+ protected void configure() {
+ bind(Bar.class).toInstance(barMock);
+ }
+ };
+ }
+
+ @Test public void testBehavior() {
+ ...
+ }
+}
+}}}
+This class creates a field for the tested class's dependencies, places in
that field a mock and binds the field into Guice with a custom Module.
+
+== Binding Fields Using BoundFieldModule ==
+{{{BoundFieldModule}}} scans a given object for fields annotated with
@Bind and binds those fields automatically. Using this, we can simplify our
{{{TestFoo}}} class to:
+{{{
+public class TestFoo {
+ // bind(Bar.class).toInstance(barMock);
+ @Bind
+ @Mock
+ private Bar barMock;
+
+ // Foo depends on Bar.
+ @Inject private Foo foo;
+
+ @Before public void setUp() {
+ barMock = ...;
+ Guice.createInjector(BoundFieldModule.of(this)).injectMembers(this);
+ }
+
+ @Test public void testBehavior() {
+ ...
+ }
+}
+}}}
+
+This binding occurrs under the following rules:
+
+ * For each {{{@Bind}}} annotated field of an object and its superclasses,
this module will bind that field's type to that field's value at injector
creation time. This includes both instance and static fields.
+ * If {{{@Bind(to = ...)}}} is specified, the field's value will be bound
to the class specified by {{{to}}} instead of the field's actual type.
+ * If a
[http://google-guice.googlecode.com/git/javadoc/com/google/inject/BindingAnnotation.html
BindingAnnotation] or
[http://atinject.googlecode.com/svn/trunk/javadoc/javax/inject/Qualifier.html
Qualifier] is present on the field, that field will be bound using that
annotation via
[http://google-guice.googlecode.com/git/javadoc/com/google/inject/binder/AnnotatedBindingBuilder.html
annotatedWith]. For example,
{{{bind(Foo.class).annotatedWith(BarAnnotation.class).toInstance(theValue)}}}.
It is an error to supply more than one
[http://google-guice.googlecode.com/git/javadoc/com/google/inject/BindingAnnotation.html
BindingAnnotation] or
[http://atinject.googlecode.com/svn/trunk/javadoc/javax/inject/Qualifier.html
Qualifier].
+ * If the field is of type
[http://google-guice.googlecode.com/git/javadoc/com/google/inject/Provider.html
Provider], the field's value will be bound as a
[http://google-guice.googlecode.com/git/javadoc/com/google/inject/Provider.html
Provider] using
[http://google-guice.googlecode.com/git/javadoc/com/google/inject/binder/LinkedBindingBuilder.html
toProvider] to the provider's parameterized type. For example,
{{{Provider<Integer>}}} binds to {{{Integer}}}. Attempting to bind a
non-parameterized {{{Provider}}} without a {{{@Bind(to = ...)}}} clause is
an error.
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