[Date Formatting] Java Default Engine AND Joda framework

A formatting string describes how date/time values should be read and written from(to) string representation

Now we compare the two kinds of formatting engines.

Engine	Formatter Thread-safe?	Description	Example
Java	SimpleDateFormat NO	Standard Java date implementation. Provides lenient, error-prone and full-featured parsing and writing. It has moderate speed and is generally a good choice unless you need to work with large quantities of date/time fields. For advanced study please refer to Java SimpleDateFormat documentation.	yyyy-MM-dd HH:mm:ss
Joda	DateTimeFormat DateTimeFormatter YES	An improved third-party date library. Joda is stricter on input data accuracy when parsing and does not work well with time zones. It does, however, provide a 20-30% speed increase compared to standard Java. For further reading please visit the project site at http://joda-time.sourceforge.net). Joda may be convenient for AS/400 machines. On the other hand, Joda is unable to read time zone expressed with any number of z letters and/or at least three Z letters in a pattern.	yyyy-MM-dd HH:mm:ss

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Java Default:
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1.1 Date Format Pattern Syntax (Java)

Letter	Date or Time Component	Presentation	Examples
G	Era designator	Text	AD
Y	Year	Year	1996; 96
M	Month in year	Month	July; Jul; VII; 07; 7
w	Week in year	Number	27
W	Week in month	Number	2
D	Day in year	Number	189
d	Day in month	Number	10
F	Day of week in month	Number	2
E	Day in week	Text	Tuesday; Tue
a	Am/pm marker	Text	PM
H	Hour in day (0-23)	Number	0
k	Hour in day (1-24)	Number	24
K	Hour in am/pm (0-11)	Number	0
h	Hour in am/pm (1-12)	Number	12
m	Minute in hour	Number	30
s	Second in minute	Number	55
S	Millisecond	Number	970
z	Time zone	General time zone	Pacific Standard Time; PST; GMT-08:00
Z	Time zone	RFC 822 time zone	-0800
'	Escape for text/id	Delimiter	(none)
''	Single quote	Literal	'

The number of symbol letters you specify also determines the format. For example, if the "zz" pattern results in "PDT", then the "zzzz" pattern generates "Pacific Daylight Time". The following table summarizes these rules:

1.2 Rules for Date Format Usage (Java)

Presentation	Processing	Number of Pattern Letters	Form
Text	Formatting	1 - 3	short or abbreviated form, if one exists
Text	Formatting	>= 4	full form
Text	Parsing	>= 1	both forms
Year	Formatting	2	truncated to 2 digits
Year	Formatting	1 or >= 3	interpreted as Number.
Year	Parsing	1	intepreted literally
Year	Parsing	2	interpreted relative to the century within 80 years before or 20 years after the time when theSimpleDateFormat instance is created
Year	Parsing	>= 3	intepreted literally
Month	Both	1-2	interpreted as a Number
Month	Parsing	>= 3	interpreted as Text (using Roman numbers, abbreviated month name - if exists, or full month name)
Month	Formatting	3	interpreted as Text (using Roman numbers, or abbreviated month name - if exists)
Month	Formatting	>= 4	interpreted as Text (full month name)
Number	Formatting	minimum number of required digits	shorter numbers are padded with zeros
Number	Parsing	number of pattern letters is ignored (unless needed to separate two adjacent fields)	any form
General time zone	Both	1-3	short or abbreviated form, if has a name. Otherwise, GMT offset value (GMT[sign][[0]0-23]:[00-59])
General time zone	Both	>= 4	full form, , if has a name. Otherwise, GMT offset value (GMT[sign][[0]0-23]:[00-59])
General time zone	Parsing	>= 1	RFC 822 time zone form is allowed
RFC 822 time zone	Both	>= 1	RFC 822 4-digit time zone format is used ([sign][0-23][00-59])
RFC 822 time zone	Parsing	>= 1	General time zone form is allowed

Examples:

1.3 Date and Time Format Patterns and Results (Java)

Date and Time Pattern	Result
"yyyy.MM.dd G 'at' HH:mm:ss z"	2001.07.04 AD at 12:08:56 PDT
"EEE, MMM d, ''yy"	Wed, Jul 4, '01
"h:mm a"	12:08 PM
"hh 'o''clock' a, zzzz"	12 o'clock PM, Pacific Daylight Time
"K:mm a, z"	0:08 PM, PDT
"yyyyy.MMMMM.dd GGG hh:mm aaa"	02001.July.04 AD 12:08 PM
"EEE, d MMM yyyy HH:mm:ss Z"	Wed, 4 Jul 2001 12:08:56 -0700
"yyMMddHHmmssZ"	010704120856-0700
"yyyy-MM-dd'T'HH:mm:ss.SSSZ"	2001-07-04T12:08:56.235-0700

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JODA:
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2.1 Date Format Pattern Syntax (Joda)

Symbol	Meaning	Presentation	Examples
G	Era designator	Text	AD
C	Century of era (>=0)	Number	20
Y	Year of era (>=0)	Year	1996
y	Year	Year	1996
x	Week of weekyear	Year	1996
M	Month of year	Month	July; Jul; 07
w	Week of year	Number	27
D	Day of year	Number	189
d	Day of month	Number	10
e	Day of week	Number	2
E	Day of week	Text	Tuesday; Tue
a	Halfday of day	Text	PM
H	Hour of day (0-23)	Number	0
k	Clockhour of day (1-24)	Number	24
K	Hour of halfday (0-11)	Number	0
h	Clockhour of halfday (1-12)	Number	12
m	Minute of hour	Number	30
s	Second of minute	Number	55
S	Fraction of second	Number	970
z	Time zone	Text	Pacific Standard Time; PST
Z	Time zone offset/id	Zone	-0800; -08:00; America/Los_Angeles
'	Escape for text/id	Delimiter	(none)
''	Single quote	Literal	'

We can see from above table, although actual format strings for Java and Joda are almost 100% compatible with each other, still there are differences. The 'F' in default java is not supported in Joda.

Basically, 'F' means 'Day of week in month', for example, '2013-11-8' is the second friday in Nov of 2013, so 'F' will get 2 as result. While 'E' means 'Day of week' only, with the same example, '2013-11-8', 'E' will get 5 as result, because it's Friday, the fifth day in the week.

The number of symbol letters you specify also determines the format. The following table summarizes these rules:

2.2 Rules for Date Format Usage (Joda)

Presentation	Processing	Number of Pattern Letters	Form
Text	Formatting	1 - 3	short or abbreviated form, if one exists
Text	Formatting	>= 4	full form
Text	Parsing	>= 1	both forms
Year	Formatting	2	truncated to 2 digits
Year	Formatting	1 or >= 3	interpreted as Number.
Year	Parsing	>= 1	intepreted literally
Month	Both	1-2	interpreted as a Number
Month	Parsing	>= 3	interpreted as Text (using Roman numbers, abbreviated month name - if exists, or full month name)
Month	Formatting	3	interpreted as Text (using Roman numbers, or abbreviated month name - if exists)
Month	Formatting	>= 4	interpreted as Text (full month name)
Number	Formatting	minimum number of required digits	shorter numbers are padded with zeros
Number	Parsing	>= 1	any form
Zone name	Formatting	1-3	short or abbreviated form
Zone name	Formatting	>= 4	full form
Time zone offset/id	Formatting	1	Offset without a colon between hours and minutes
Time zone offset/id	Formatting	2	Offset with a colon between hours and minutes
Time zone offset/id	Formatting	>= 3	Full textual form like this: "Continent/City"
Time zone offset/id	Parsing	1	Offset without a colon between hours and minutes
Time zone offset/id	Parsing	2	Offset with a colon between hours and minutes

For more details, the official docs are the best place to go.

Reference:
Micosoft: StandardDate and Time Format Strings

Joda: User Guide

Java Doc of SimpleDateFormat

One good summarization found on the internet

Java-Path Topic 1 =>Get resource based on classpath [ this.getClass().getResource() AND this.getClass().getClassLoader().getResource() ]

For java developers, must be very familar to these two methods, 'this.getClass().getResource()' and 'this.getClass().getClassLoader().getResource()'.

For new comers, one most frustrating issue is 'The file is obviously there, but the code just can't find it...Damn it. :) '.

Based on the daily work and study, I have a feeling that, to have a good understanding of how things works can help a lot when you want to use those things.

High buildings are always built on firm foundations. Just take some time to read the doc or source code when you have doubts. All the daily accumulations will contribute to better understanding. OK, stop all the craps.

To get resources based on classpath, there are basically three ways:

URL url = this.getClass().getResource("resource_name");

URL url = this.getClass().getClassLoader().getResource("resource_name");

URL url = Thread.currentThread().getContextClassLoader().getResource("resource_name");

The 1st one,

URL url = this.getClass().getResource("resource_name");

This is to get resource based on current class instance. But, if we check the source code of this method, we'll see that actually we still get the resource using classloader.

/**
     * Finds a resource with a given name.  The rules for searching resources
     * associated with a given class are implemented by the defining
     * {@linkplain ClassLoader class loader} of the class.  This method
     * delegates to this object's class loader.  If this object was loaded by
     * the bootstrap class loader, the method delegates to {@link
     * ClassLoader#getSystemResource}.
     *
     * <p> Before delegation, an absolute resource name is constructed from the
     * given resource name using this algorithm:
     *
     * <ul>
     *
     * <li> If the <tt>name</tt> begins with a <tt>'/'</tt>
     * (<tt>'&#92;u002f'</tt>), then the absolute name of the resource is the
     * portion of the <tt>name</tt> following the <tt>'/'</tt>. 
     *
     * <li> Otherwise, the absolute name is of the following form:
     *
     * <blockquote><pre>
     *   <tt>modified_package_name</tt>/<tt>name</tt>
     * </pre></blockquote>
     *
     * <p> Where the <tt>modified_package_name</tt> is the package name of this
     * object with <tt>'/'</tt> substituted for <tt>'.'</tt>
     * (<tt>'&#92;u002e'</tt>).
     *
     * </ul>
     *
     * @param  name name of the desired resource
     * @return      A  {@link java.net.URL} object or <tt>null</tt> if no
     *              resource with this name is found
     * @since  JDK1.1
     */
    public java.net.URL getResource(String name) {
        name = resolveName(name);
        ClassLoader cl = getClassLoader0();
        if (cl==null) {
            // A system class.
            return ClassLoader.getSystemResource(name);
        }
        return cl.getResource(name);
    }

And, in the resolveName(name) method:

/**
     * Add a package name prefix if the name is not absolute Remove leading "/"
     * if name is absolute
     */
    private String resolveName(String name) {
        if (name == null) {
            return name;
        }
        if (!name.startsWith("/")) {
            Class c = this;
            while (c.isArray()) {
                c = c.getComponentType();
            }
            String baseName = c.getName();
            int index = baseName.lastIndexOf('.');
            if (index != -1) {
                name = baseName.substring(0, index).replace('.', '/')
                    +"/"+name;
            }
        } else {
            name = name.substring(1);
        }
        return name;
    }

Based on these, we can have the conclusion that:

*****
1. If the passed in resource name is starting with slash '/', the input path is relative to the classpath.

Attention: If you are running a test case, and if the test classpath have exactly the same resource with the main classpath, then the one on the test classpath will be used. If the test classpath does not have the resource, the main classpath will be used.


2. If the passed in resource name does not start with slash '/'. Then the method resolveName will add the package to the path. So in this case, the path is relative to current package path.
*****

Example:

package com.test;

import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

import org.junit.Test;

public class PathTest {

    @Test
    public void test() {
        
        
        System.out.println("For=> this.getClass().getResource");
        
        String path = "test.properties";
        System.out.println("'"+path+"' => "+this.getClass().getResource(path));
        InputStream in = this.getClass().getResourceAsStream(path);
        System.out.println("Property Version => " + loadFile(in));
        
        path = "/com/test/test.properties";
        System.out.println("'"+path+"' => "+this.getClass().getResource(path));
        in = this.getClass().getResourceAsStream(path);
        System.out.println("Property Version => " + loadFile(in));
        
        path = "/test/test.properties";
        System.out.println("'"+path+"' => "+this.getClass().getResource(path));
        in = this.getClass().getResourceAsStream(path);
        System.out.println("Property Version => " + loadFile(in));
        
        path = "";
        System.out.println("'"+path+"' => "+this.getClass().getResource(path));
        
        path = "/";
        System.out.println("'"+path+"' => "+this.getClass().getResource(path));
        
        path = "/test";
        System.out.println("'"+path+"' => "+this.getClass().getResource(path));
        
        path = "/non-test";
        System.out.println("'"+path+"' => "+this.getClass().getResource(path));
        
        path = "/non-test-emptyfolder";
        System.out.println("'"+path+"' => "+this.getClass().getResource(path));
        
        path = "test-emptyfolder";
        System.out.println("'"+path+"' => "+this.getClass().getResource(path));
        
        path = "/test-emptyfolder";
        System.out.println("'"+path+"' => "+this.getClass().getResource(path));
        
        
    }
    
    public String loadFile(InputStream in){
        
        Properties prop = new Properties();
        try {
            prop.load(in);
            return (String) prop.get("test.version");
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

}

Output:

For=> this.getClass().getResource
'test.properties' => file:/C:/stsworkspace/test-code/target/classes/com/test/test.properties
Property Version => 5.0(src/main/java/come.test/test.properties)
'/com/test/test.properties' => file:/C:/stsworkspace/test-code/target/classes/com/test/test.properties
Property Version => 5.0(src/main/java/come.test/test.properties)
'/test/test.properties' => file:/C:/stsworkspace/test-code/target/classes/test/test.properties
Property Version => 1.0(src/main/resources/test.properties)
'' => file:/C:/stsworkspace/test-code/target/test-classes/com/test/
'/' => file:/C:/stsworkspace/test-code/target/test-classes/
'/test' => file:/C:/stsworkspace/test-code/target/test-classes/test
'/non-test' => file:/C:/stsworkspace/test-code/target/classes/non-test
'/non-test-emptyfolder' => null
'test-emptyfolder' => null
'/test-emptyfolder' => null

Above is the result when we run in IDE, but if we run the test case using maven, there will be problem. Because, when maven do the packaging, by default it'll remove all the non-class files in the package because it expects you to put all the resources under src/main/resources. Also, it'll ignore all the empty folders under resources.

After we package the project:

In the target folder we can see that:

Inside classes folder:

Inside test-classes folder:

==========================================Beautiful Line Break======================================

The 2nd one,

URL url = this.getClass().getClassLoader().getResource("resource_name");

This is to get the resource using classloader. By looking into the source code, we can see that it'll go all the way up to get the parent class loader. Regarding the classloader part, I'll not include details now, I still more research on the basic JVM knowledge.

/**
     * Finds the resource with the given name.  A resource is some data
     * (images, audio, text, etc) that can be accessed by class code in a way
     * that is independent of the location of the code.
     *
     * <p> The name of a resource is a '<tt>/</tt>'-separated path name that
     * identifies the resource.
     *
     * <p> This method will first search the parent class loader for the
     * resource; if the parent is <tt>null</tt> the path of the class loader
     * built-in to the virtual machine is searched.  That failing, this method
     * will invoke {@link #findResource(String)} to find the resource.  </p>
     *
     * @param  name
     *         The resource name
     *
     * @return  A <tt>URL</tt> object for reading the resource, or
     *          <tt>null</tt> if the resource could not be found or the invoker
     *          doesn't have adequate  privileges to get the resource.
     *
     * @since  1.1
     */
    public URL getResource(String name) {
    URL url;
    if (parent != null) {
        url = parent.getResource(name);
    } else {
        url = getBootstrapResource(name);
    }
    if (url == null) {
        url = findResource(name);
    }
    return url;
    }

Attention:

 If one class is loaded by bootstrap loader, then sometimes it'll return null when we get the classloader. For example, if we use 'new Object().getClass().getClassLoader()', it may return null. If we use this classloader to load resource, it'll throw null pointer exception. So to make it safe, we better use 'this.getClass().getClassLoader()'.

Normally if we don't specify special classloader in our project. The class that we write ourselves will be loaded using 'ClassLoader.getSystemClassLoader()'.

*****
So, in the second way, the resource path that passed in should be relative to the classpath.
And it does not support absolute path.

Attention: If you are running a test case, and if the test classpath have exactly the same resource with the main classpath, then the one on the test classpath will be used. If the test classpath does not have the resource, the main classpath will be used.
*****

Example:

System.out.println();
        System.out.println("For=> this.getClass().getClassLoader().getResource");
        
        path = "test/test.properties";
        System.out.println("'"+path+"' => "+this.getClass().getClassLoader().getResource(path));
        in = this.getClass().getClassLoader().getResourceAsStream(path);
        System.out.println("Property Version => " + loadFile(in));
        
        path = "com/test/test.properties";
        System.out.println("'"+path+"' => "+this.getClass().getClassLoader().getResource(path));
        in = this.getClass().getClassLoader().getResourceAsStream(path);
        System.out.println("Property Version => " + loadFile(in));
        
        path = "com/test/test.properties";
        System.out.println("'"+path+"' => "+this.getClass().getClassLoader().getResource(path));
        in = this.getClass().getClassLoader().getResourceAsStream(path);
        System.out.println("Property Version => " + loadFile(in));
        
        path = "";
        System.out.println("'"+path+"' => "+this.getClass().getClassLoader().getResource(path));
        
        path = "/";
        System.out.println("'"+path+"' => "+this.getClass().getClassLoader().getResource(path));
        
        path = "test";
        System.out.println("'"+path+"' => "+this.getClass().getClassLoader().getResource(path));
        
        path = "/test";
        System.out.println("'"+path+"' => "+this.getClass().getClassLoader().getResource(path));
        
        path = "non-test";
        System.out.println("'"+path+"' => "+this.getClass().getClassLoader().getResource(path));
        
        path = "/non-test";
        System.out.println("'"+path+"' => "+this.getClass().getClassLoader().getResource(path));
        
        path = "non-test-emptyfolder";
        System.out.println("'"+path+"' => "+this.getClass().getClassLoader().getResource(path));
        
        path = "/non-test-emptyfolder";
        System.out.println("'"+path+"' => "+this.getClass().getClassLoader().getResource(path));
        
        path = "test-emptyfolder";
        System.out.println("'"+path+"' => "+this.getClass().getClassLoader().getResource(path));
        
        path = "/test-emptyfolder";
        System.out.println("'"+path+"' => "+this.getClass().getClassLoader().getResource(path));

Output:

For=> this.getClass().getClassLoader().getResource
'test/test.properties' => file:/C:/stsworkspace/test-code/target/classes/test/test.properties
Property Version => 1.0(src/main/resources/test.properties)
'com/test/test.properties' => file:/C:/stsworkspace/test-code/target/classes/com/test/test.properties
Property Version => 5.0(src/main/java/come.test/test.properties)
'com/test/test.properties' => file:/C:/stsworkspace/test-code/target/classes/com/test/test.properties
Property Version => 5.0(src/main/java/come.test/test.properties)
'' => file:/C:/stsworkspace/test-code/target/test-classes/
'/' => null
'test' => file:/C:/stsworkspace/test-code/target/test-classes/test
'/test' => null
'non-test' => file:/C:/stsworkspace/test-code/target/classes/non-test
'/non-test' => null
'non-test-emptyfolder' => null
'/non-test-emptyfolder' => null
'test-emptyfolder' => null
'/test-emptyfolder' => null

Again, Above is the result when we run in IDE, if we run the test case using maven, there will be problem.

Junit Config @ContextConfiguration locations

When we run Junit test for services, if the service is configured using spring, we need to load the spring context first.

Normally, the way to configure the Junit test case is:

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations={"config.xml"})
public class MessageServiceTest {

 private static final Logger logger = Logger.getLogger(MessageServiceTest.class);
 
 //MessageService service = new MessageServiceImpl();
 
 @Autowired
 MessageService service;
 
 @Test
 public void sendMessageTest() {
        //TODO-something
        }
}

If we are not clear of how spring look for context file, it's boring to have exceptions files not found blablabla...

Just make a summary here:

@ContextConfiguration(locations={"config.xml"})

=>This means to look for config.xml under the test package that holds currently running test case.

@ContextConfiguration(locations={"/config.xml"})

@ContextConfiguration(locations={"classfile:config.xml"})

=>These two equals, means to look for config.xml under the classpath. It could be under either 'src/main/resources' or 'src/test/resources' (By default) (If you change the classpath, then configure based on your own configuration.)

@ContextConfiguration(locations={"file:src/main/webapp/config.xml"})

=>This means to look for config.xml based on relative path to the project's base directory.


If wanna configure multiple config files, then

@ContextConfiguration
(
  {
   "classpath:beans.xml",
   "file:src/main/webapp/spring/applicationContext.xml",
   "file:src/main/webapp/spring/domain-config.xml",
   "file:src/main/webapp/spring/dispatcher-servlet.xml"
  }
)

Good Luck!