de.weltraumschaf.commons.application

Class IOStreams

java.lang.Object

de.weltraumschaf.commons.application.IOStreams

All Implemented Interfaces:

IO

public final class IOStreams
extends Object
implements IO

Immutable aggregate object which contains STDIN, STDOUT and STDERR streams.

It is not good practice to clutter production code with calls to System.out, System.err, and System.in. But on the other hand most applications must do I/O to the user. This aggregate object contains I/O streams to pass around as injected dependency. It is only necessary to the systems IO only at the main applications entry point:

public void main(final String[] args) {
      final IOStreams io = new IOStreams(System.in, System.out, System.err);

      // Pass around the io object to your client code.

      System.exit(0);
 }
 

In the test code it will be easy to replace the I/O with mocks:

@Test public void someTestWithIO() {
      final IOStreams io = new IOStreams(mock(InputStream.class),
                                   mock(PrintStream.class),
                                   mock(PrintStream.class));

      // Pass around the io object to your client code and assert something.
 }
 

As a convenience method for creating an I/O streams object with the default I/O streams of System you can use newDefault().

Since:

1.0.0

Author:

Sven Strittmatter

Field Summary

Fields

Modifier and Type	Field and Description
static String	DEFAULT_ENCODING Default character encoding for out put print streams.
private PrintStream	stderr Standard error stream.
private InputStream	stdin Standard input stream.
private PrintStream	stdout Standard output stream.

Constructor Summary

Constructors

Constructor and Description
IOStreams(InputStream stdin, PrintStream stdout, PrintStream stderr) Initializes the streams.

Method Summary

Methods

Modifier and Type	Method and Description
void	error(String str) Prints error.
void	errorln(String str) Prints error line.
PrintStream	getStderr() Get standard errorln output stream.
InputStream	getStdin() Get standard input stream.
PrintStream	getStdout() Get standard output stream.
static IOStreams	newDefault() Creates same as newDefault(java.lang.String) but with DEFAULT_ENCODING as encoding.
static IOStreams	newDefault(String encoding) Creates a new streams object initialized with System.in, System.out, and System.err.
void	print(String str) Prints string.
void	println(String str) Prints string line.
void	printStackTrace(Throwable ex) Prints exception stack trace.

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_ENCODING

public static final String DEFAULT_ENCODING

Default character encoding for out put print streams.

See Also:

Constant Field Values

stdin

private final InputStream stdin

Standard input stream.

stdout

private final PrintStream stdout

Standard output stream.

stderr

private final PrintStream stderr

Standard error stream.

Constructor Detail

IOStreams

public IOStreams(InputStream stdin,
         PrintStream stdout,
         PrintStream stderr)

Initializes the streams.

Parameters:

stdin - must not be null

stdout - must not be null

stderr - must not be null

Method Detail

getStderr

public PrintStream getStderr()

Get standard errorln output stream.

Specified by:

getStderr in interface IO

Returns:

Print stream object.

getStdin

public InputStream getStdin()

Get standard input stream.

Specified by:

getStdin in interface IO

Returns:

Input stream object.

getStdout

public PrintStream getStdout()

Get standard output stream.

Specified by:

getStdout in interface IO

Returns:

Print stream object.

newDefault

public static IOStreams newDefault()
                            throws UnsupportedEncodingException

Creates same as newDefault(java.lang.String) but with DEFAULT_ENCODING as encoding.

Returns:

Return always new instance.

Throws:

UnsupportedEncodingException - If system does not support encoding.

newDefault

public static IOStreams newDefault(String encoding)
                            throws UnsupportedEncodingException

Creates a new streams object initialized with System.in, System.out, and System.err. The output "print streams" get DEFAULT_ENCODING as encoding set. Also the System.out, and System.err are changed with a copy of the original print stream with the encoding.

Parameters:

encoding - must not be null or empty

Returns:

return always new instance

Throws:

UnsupportedEncodingException - if system does not support passed encoding

printStackTrace

public void printStackTrace(Throwable ex)

Prints exception stack trace.

Specified by:

printStackTrace in interface IO

Parameters:

ex - must not be null

errorln

public void errorln(String str)

Prints error line.

Specified by:

errorln in interface IO

Parameters:

str - String to print.

error

public void error(String str)

Prints error.

Specified by:

error in interface IO

Parameters:

str - String to print.

println

public void println(String str)

Prints string line.

Specified by:

println in interface IO

Parameters:

str - String to print.

print

public void print(String str)

Prints string.

Specified by:

print in interface IO

Parameters:

str - String to print.