org.apache.beam.sdk.util

Class InstanceBuilder<T>

java.lang.Object

org.apache.beam.sdk.util.InstanceBuilder<T>

Type Parameters:

T - type type of object returned by this instance builder

public class InstanceBuilder<T>
extends java.lang.Object

Utility for creating objects dynamically.

Method Summary

Modifier and Type	Method and Description
T	build() Creates the instance by calling the factory method with the given arguments.
InstanceBuilder<T>	fromClass(java.lang.Class<?> factoryClass) Sets the factory class to use for instance construction.
InstanceBuilder<T>	fromClassName(java.lang.String name) Sets the class name to be constructed.
InstanceBuilder<T>	fromFactoryMethod(java.lang.String methodName) Sets the name of the factory method used to construct the instance.
static <T> InstanceBuilder<T>	ofType(java.lang.Class<T> type) Create an InstanceBuilder for the given type.
static <T> InstanceBuilder<T>	ofType(TypeDescriptor<T> token) Create an InstanceBuilder for the given type.
<ArgT> InstanceBuilder<T>	withArg(java.lang.Class<? super ArgT> argType, ArgT value) Adds an argument to be passed to the factory method.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

ofType

public static <T> InstanceBuilder<T> ofType(java.lang.Class<T> type)

Create an InstanceBuilder for the given type.

The specified type is the type returned by build(), which is typically the common base type or interface of the instance being constructed.

ofType

public static <T> InstanceBuilder<T> ofType(TypeDescriptor<T> token)

Create an InstanceBuilder for the given type.

The specified type is the type returned by build(), which is typically the common base type or interface for the instance to be constructed.

The TypeDescriptor argument allows specification of generic types. For example, a List<String> return type can be specified as ofType(new TypeDescriptor<List<String>>(){}).

fromClassName

public InstanceBuilder<T> fromClassName(java.lang.String name)
                                 throws java.lang.ClassNotFoundException

Sets the class name to be constructed.

If the name is a simple name (ie Class.getSimpleName()), then the package of the return type is added as a prefix.

The default class is the return type, specified in ofType(java.lang.Class<T>).

Modifies and returns the InstanceBuilder for chaining.

Throws:

java.lang.ClassNotFoundException - if no class can be found by the given name

fromClass

public InstanceBuilder<T> fromClass(java.lang.Class<?> factoryClass)

Sets the factory class to use for instance construction.

Modifies and returns the InstanceBuilder for chaining.

fromFactoryMethod

public InstanceBuilder<T> fromFactoryMethod(java.lang.String methodName)

Sets the name of the factory method used to construct the instance.

The default, if no factory method was specified, is to look for a class constructor.

Modifies and returns the InstanceBuilder for chaining.

withArg

public <ArgT> InstanceBuilder<T> withArg(java.lang.Class<? super ArgT> argType,
                                         ArgT value)

Adds an argument to be passed to the factory method.

The argument type is used to lookup the factory method. This type may be a supertype of the argument value's class.

Modifies and returns the InstanceBuilder for chaining.

Type Parameters:

ArgT - the argument type

build

public T build()

Creates the instance by calling the factory method with the given arguments.

Defaults

• factory class: defaults to the output type class, overridden via fromClassName(String).
• factory method: defaults to using a constructor on the factory class, overridden via fromFactoryMethod(String).

Throws:

java.lang.RuntimeException - if the method does not exist, on type mismatch, or if the method cannot be made accessible.