Java, Rest, Soap, Spring

Front 1

GET

Back 1

– use it to fetch a resourceThe GET verb denotes the only method that can be cached at multiple levels. Resources can be cached at the origin, at the client and in between. Network devices can participate in the caching strategy, in turn significantly reducing the load on the origin service.

Front 2

POST

Back 2

– use it to create a resourceThe POST verb denotes the creation of a resource. This method is not cacheable and is the most dangerous of all. Using this method guaranties that the system state will be modified.It can also be used to push data to the service. When the service receives the data, it can create a new resource returning the URI corresponding to the new resource. It can react to the received data in various unpredictable ways.

Front 3

PUT

Back 3

– use it to update a resourceThe PUT verb denotes the modification of a resource state. The difference between PUT and POST, is that PUT modifies the resource state in anidempotent manner. No matter how many times a PUT gets executed, the outcome is always the same and predictable.PUT allows you to push a resource to a specific URI. If the resource does not exist it creates it. If it exists it replaces it.

Front 4

HEAD

Back 4

– use it to retrieve meta-information without the response bodyThe HEAD verb is very useful. It can be used to fetch E-Tags and other meta-information for specific resources without the full representational state of the requested resource. This empowers the consumers to verify if a specific resource has been modified since the last time it was fetched. Further more, this is a great trick to help reduce the amount of data required to travel over the network for each request.PATCH

Front 5

PATCH

Back 5

– use it to make partial modifications to resourcesRarely have I seen this verb used but I’m sure it comes in handy when a consumer is required to send a delta of the original and the modified representational state to the server. In turn reducing the amount of data required to travel over the network and giving the consumer a better experience.

Front 6

Hypermedia

Back 6

– use it to make partial modifications to resourcesRarely have I seen this verb used but I’m sure it comes in handy when a consumer is required to send a delta of the original and the modified representational state to the server. In turn reducing the amount of data required to travel over the network and giving the consumer a better experience.

Front 7

HAL

Back 7

HAL is a simple way of linking with JSON or XML.It provides a set of conventions for expressing hyperlinks to, and embeddedness of, related resources – the rest of a HAL document is just plain old JSON or XML.HAL is a bit like HTML for machines, in that it is designed to drive many different types of application. The difference is that HTML is intended for presenting a graphical hypertext interface to a ‘human actor’, whereas HAL is intended for presenting a machine hypertext interface to ‘automated actors’.

Front 8

PUT vs. POST

Back 8

PUT vs POST in REST. In other words, POST is used to create. The PUT method requests that the enclosed entity be stored under the supplied Request-URI . If the Request-URI refers to an already existing resource, the enclosed entity SHOULD be considered as a modified version of the one residing on the origin server.

Front 9

SOAP (not REST)

Back 9

SOAP defines the XML-based message format that Web service-enabled applicationsuse to communicate and inter-operate with each other over the Web.

Front 10

WSDL (used with SOAP)

Back 10

Part of the magic is the Web Services Description Language (WSDL). This is another file that’s associated with SOAP. It provides a definition of how the Web service works, so that when you create a reference to it, the IDE can completely automate the process. So, the difficulty of using SOAP depends to a large degree on the language you use.

Front 11

Error handling in SOAP

Back 11

built in so easy to handle errors

Front 12

REST - definition / benefits

Back 12

REST provides a lighter weight alternative. Instead of using XML to make a request, REST relies on a simple URL in many cases. In some situations you must provide additional information in special ways, but most Web services using REST rely exclusively on obtaining the needed information using the URL approach. REST can use four different HTTP 1.1 verbs (GET, POST, PUT, and DELETE) to perform tasks

Front 13

Difference in data types SOAP vs. REST

Back 13

Unlike SOAP, REST doesn’t have to use XML to provide the response. You can find REST-based Web services that output the data in Command Separated Value (CSV), JavaScript Object Notation (JSON) and Really Simple Syndication (RSS).

Front 14

Argument of SOAP vs. REST

Back 14

SOAP is definitely the heavyweight choice for Web service access. It provides the following advantages when compared to REST:

Language, platform, and transport independent (REST requires use of HTTP)

Works well in distributed enterprise environments (REST assumes direct point-to-point communication)

StandardizedProvides significant pre-build extensibility in the form of the WS* standards

Built-in error handlingAutomation when used with certain language products

REST is easier to use for the most part and is more flexible.

It has the following advantages when compared to SOAP:

No expensive tools require to interact with the Web service

Smaller learning curveEfficient (SOAP uses XML for all messages, REST can use smaller message formats)

Fast (no extensive processing required)

Closer to other Web technologies in design philosophy

Front 15

What do you need to do for a connection to a URL and get data?

Back 15

URL oracle = new

URL("http://www.oracle.com/");

URLConnection yc = oracle.openConnection();

BufferedReader in = new BufferedReader(new InputStreamReader( yc.getInputStream()));

String inputLine;

while ((inputLine = in.readLine()) != null) System.out.println(inputLine); in.close();

Front 16

Given a string, return a new string where the first and last chars have been exchanged.

Back 16

public String frontBack(String str) {

if (str.length() <= 1) return str;

String mid = str.substring(1, str.length()-1);

// last + mid + first return str.charAt(str.length()-1) + mid + str.charAt(0);

}

Front 17

Given a string, we'll say that the front is the first 3 chars of the string. If the string length is less than 3, the front is whatever is there. Return a new string which is 3 copies of the front.

Back 17

public String front3(String str) {

String front;

if (str.length() >= 3) {

front = str.substring(0, 3);

} else {

front = str;

}

return front + front + front;

}

Front 18

Given a string, take the last char and return a new string with the last char added at the front and back, so "cat" yields "tcatt". The original string will be length 1 or more.

Back 18

public String backAround(String str) {

// Get the last char String last = str.substring(str.length() - 1);

return last + str + last;

}

Front 19

Return true if the given non-negative number is a multiple of 3 or a multiple of 5. Use the % "mod" operator

Back 19

public boolean or35(int n)

{

return (n % 3 == 0) || (n % 5 == 0);

}

Front 20

Given a string, take the first 2 chars and return the string with the 2 chars added at both the front and back, so "kitten" yields"kikittenki". If the string length is less than 2, use whatever chars are there.

Back 20

public String front22(String str) {

// First figure the number of chars to take int take = 2;

if (take > str.length()) {

take = str.length();

}

String front = str.substring(0, take);

return front + str + front;

}

Front 21

Given a string, return a new string where "not " has been added to the front. However, if the string already begins with "not", return the string unchanged. Note: use .equals() to compare 2 strings.

Back 21

public String notString(String str) {

if (str.length() >= 3 && str.substring(0, 3).equals("not"))

{

return str;

}

return "not " + str;

}

Front 22

package supports regular expression processing

Back 22

java.util.regex

Front 23

what do you use for regular expressions in Java?

Back 23

the Pattern and Matcher classes

use the compile function on the pattern instance

Front 24

Regex example - matches any word

Back 24

String regex = "\\w+";

Pattern pattern = Pattern.compile(regex);

String candidate = "asdf Java2s.com";

Matcher matcher = pattern.matcher(candidate);

if (matcher.find()) { System.out.println("GROUP 0:" + matcher.group(0));

}

Front 25

Reg ex example

Back 25

String regex = "[a-z]@.";

Pattern p = Pattern.compile(regex);

String str = "[e-mail],[e-mail],[e-mail]";

Matcher m = p.matcher(str);

if (m.find()) {

String foundStr = str.substring(m.start(), m.end());

System.out.println("Found string is:" + foundStr);

}

Front 26

what does the overloaded 2 argument pattern.compile method do?

Back 26

sets options on the pattern. IE - Pattern.LITERAL

Front 27

Key parts of REG EX

Back 27

Pattern p = Pattern.compile(regex);

Matcher m = p.matcher(source);

while (m.find()) {

System.out.println("Matched Text:" + m.group() + ", Start:" + m.start() + ", " + "End:" + m.end());

}

OUTPUT:

Matched Text: c@e Start:2 End:2

Front 28

Java I/O File example

Back 28

File f = new File(pathname); System.out.println("File Name: " + f.getName()); System.out.println("File exists: " + f.exists()); System.out.println("Absolute Path: " + f.getAbsolutePath());

Front 29

Creating a File - Java Code

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File dummyFile = new File("test.txt");

boolean fileCreated = dummyFile.createNewFile();

Front 30

Creating a file in the TMP directory

Back 30

File tempFile = File.createTempFile("abc", ".txt");

Front 31

New Directory Java code

Back 31

File newDir = new File("C:\\users\\home");

newDir.mkdir();

Front 32

List of files in a root directories - code

Back 32

File[] roots = File.listRoots(); System.out.println("List of root directories:");

for (File f : roots) { System.out.println(f.getPath());

}

Front 33

List of files and directories

Back 33

// Change the dirPath value to list files from your directory

String dirPath = "C:\\";

File dir = new File(dirPath);

File[] list = dir.listFiles();

for (File f : list) {

if (f.isFile())

{ System.out.println(f.getPath() + " (File)"); } else if (f.isDirectory()) { System.out.println(f.getPath() + " (Directory)"); } }

Front 34

Filefilter written in lambda exp

Back 34

FileFilter filter = file -> {

if (file.isFile()) {

String fileName = file.getName().toLowerCase(); if (fileName.endsWith(".sys")) {

return false;

} }

return true;

};

Front 35

Using a FileFilter

Back 35

FileFilter filter = file -> {

if (file.isFile()) {

String fileName = file.getName().toLowerCase();

if (fileName.endsWith(".sys")) {

return false; }

}

return true;

};

File[] list = dir.listFiles(filter);

Front 36

Reading data from a file

Back 36

String dataSourceFile = "asdf.txt";

try (

FileInputStream fin = new FileInputStream(dataSourceFile))

{

byte byteData;

while ((byteData = (byte) fin.read()) != -1) { System.out.print((char) byteData);

}

} catch (FileNotFoundException e) {

; } catch (IOException e) {

e.printStackTrace();

}

}

Front 37

Getting a File input stream

Back 37

try (

FileInputStream fin = new FileInputStream(dataSourceFile)

) {

Front 38

Use this. Buffered Input Stream code ex.

Back 38

String srcFile = "test.txt";

try (

BufferedInputStream bis = new BufferedInputStream(new FileInputStream( srcFile))

) {

// Read one byte at a time and display it byte byteData;

while ((byteData = (byte) bis.read()) != -1) { System.out.print((char) byteData); }

} catch (Exception e2) {

e2.printStackTrace(); }

Front 39

Buffered Output Stream

Back 39

has better speed...

BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("your output file path");

then can use write(), flush(), and close() methods

Front 40

Writing to a File

Back 40

// Get the line separator for the current platform

String lineSeparator = System.getProperty("line.separator");

String line1 = "test"; String line2 = "test1"; String line3 = "test2"; String line4 = "test3";

try (

FileOutputStream fos = new FileOutputStream(destFile))

{ fos.write(line1.getBytes()); fos.write(lineSeparator.getBytes()); fos.write(line2.getBytes()); fos.write(lineSeparator.getBytes()); fos.write(line3.getBytes()); fos.write(lineSeparator.getBytes()); fos.write(line4.getBytes());

// Flush the written bytes to the file

fos.flush();

System.out.println("Text has been written to " + (new File(destFile)).getAbsolutePath());

} catch (Exception e2) {

e2.printStackTrace();

}

Front 41

PrintStream - definition

Back 41

The PrintStream class is a concrete decorator for the output stream.

PrintStream can print any data type values, primitive or object, in a suitable format for printing.

PrintStream can write data to the output stream do not throw an IOException.

If a method throws an IOException, PrintStream sets an internal flag, rather than throwing the exception to the caller.

The flag can be checked using its checkError() method, which returns true if an IOException occurs during the method execution.

PrintStream has an auto-flush capability. We can specify in its constructor that it should flush the contents written to it automatically.

Front 42

PrintStream example

Back 42

String destFile = "luci3.txt";

try (

PrintStream ps = new PrintStream(destFile))

{

ps.println("test");

ps.println("test1");

ps.println("test2");

ps.print("test3");

// flush the print stream

ps.flush();

System.out.println("Text has been written to " + (new File(destFile).getAbsolutePath()));

} catch (FileNotFoundException e1) { e1.printStackTrace();

}

Front 43

DataOutputStream - def

Back 43

DataOutputStream can write Java primitive data type values to an output stream.

The DataOutputStream class contains a write method to write a data type. It supports writing a string to an output stream using the writeUTF(String text) method.

To write Java primitive data type values to a file named primitives.dat, we construct an object of DataOutputStream as follows:

DataOutputStream dos = new DataOutputStream(new FileOutputStream("primitives.dat"));

Front 44

DataOutputStream ex.

Back 44

try (

DataOutputStream dos = new DataOutputStream(new FileOutputStream( destFile))) {

dos.writeInt(765);

dos.writeDouble(6789.50); dos.writeBoolean(true);

dos.writeUTF("Java Input/Output is cool!");

Front 45

Java pipes code

Back 45

PipedInputStream pis = new PipedInputStream();

PipedOutputStream pos = new PipedOutputStream();

pis.connect(pos);

/* Connect the two ends */

Front 46

Piped I/O example

Back 46

PipedInputStream pis = new PipedInputStream();

PipedOutputStream pos = new PipedOutputStream();

pos.connect(pis);

Runnable producer = () -> produceData(pos); Runnable consumer = () -> consumeData(pis); new Thread(producer).start();

new Thread(consumer).start();

}

public static void produceData(PipedOutputStream pos) {

try {

for (int i = 1; i <= 50; i++) {

pos.write((byte) i);

pos.flush();

System.out.println("Writing: " + i); Thread.sleep(500);

}

pos.close();

} catch (Exception e) {

e.printStackTrace();

} }

public static void consumeData(PipedInputStream pis) {

try {

int num = -1;

while ((num = pis.read()) != -1) { System.out.println("Reading: " + num); } pis.close();

} catch (Exception e) {

e.printStackTrace();

}

Front 47

Serializing an object code ex.

Back 47

File fileObject = new File("person.ser");

try (

ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream( fileObject))) {

oos.writeObject(p1);

oos.writeObject(p2);

oos.writeObject(p3);

Front 48

implementation of load() and dump() for a JSON serializable object

Back 48

public JSONObject dump() throws JSONException {

JSONObject result = new JSONObject(); JSONArray a = new JSONArray();

for(T i : items){ a.put(i.dump());

// inside this i.dump(), store "class-name" } result.put("items", a); return result;}public void load(JSONObject obj) throws JSONException {

JSONArray arrayItems = obj.getJSONArray("items");

for (int i = 0; i < arrayItems.length(); i++) { JSONObject item = arrayItems.getJSONObject(i);

String className = item.getString("class-name");

try { Class clazzy = Class.forName(className); T newItem = (T) clazzy.newInstance(); newItem.load(obj); items.add(newItem);

} catch (InstantiationException e) {

// whatever } catch (IllegalAccessException e) {

// whatever } catch (ClassNotFoundException e) {

// whatever }

Front 49

What interface do you need to implement to Serialize your class in JSON?

Back 49

interface JSONSerializable{

public JSONObject dump() throws JSONException

//serializes object

public void load(JSONObject obj) throws JSONException

//deserializes object

}

Front 50

BufferReader code example

Back 50

BufferedReader br = new BufferedReader(new LowerCaseReader(new FileReader( fileName)));

String str = null;

while ((str = br.readLine()) != null) {

System.out.println(str);

}

Front 51

Aspect-Oriented Programming

Back 51

AOP provides the ability to implement crosscutting logic, which applies to many parts of your application, in a single place.

Front 52

JAXB

Back 52

JAXB: The newest implementation to read XML documents: Is part of Java 6 in v2.

This allows us to serialize java objects from a document. You read the document with a class that implements an interface to javax.xml.bind.Unmarshaller (you get a class for this from JAXBContext.newInstance).

The context has to be initialized with the used classes, but you just have to specify the root classes and don't have to worry about static referenced classes.

You use annotations to specify which classes should be elements (@XmlRootElement) and which fields are elements(@XmlElement) or attributes (@XmlAttribute, what a surprise!)

RootElementClass adr = new RootElementClass();

FileInputStream adrFile = null;

try {

adrFile = new FileInputStream("test"); JAXBContext ctx = JAXBContext.newInstance(RootElementClass.class);

Unmarshaller um = ctx.createUnmarshaller(); adr = (RootElementClass) um.unmarshal(adrFile);

} catch(IOException exc) { } catch(JAXBException exc) { } finally { }Write document: FileOutputStream adrFile = null; try { adrFile = new FileOutputStream("test.xml"); JAXBContext ctx = JAXBContext.newInstance(RootElementClass.class); Marshaller ma = ctx.createMarshaller(); ma.marshal(..); } catch(IOException exc) { } catch(JAXBException exc) { } finally { }

Front 53

Spring Project with Wired Beans

Back 53

By using Spring Dependency Injection (DI) we can declare Java Beans in the Spring configuration xml file. Then wire the Java Beans in the xml file. In this way Spring can make our printer loosely coupled to the different Printer implementations.We change the Helper class to accept the Printer.package

com.java2s.output;

import com.java2s.output.Printer;

public class OutputHelper{

Printer outputGenerator;

public void print(){ outputGenerator.print(); } public void setOutputGenerator(Printer outputGenerator){

this.outputGenerator = outputGenerator; }

}

Then we have to create a Spring bean configuration file and declare all your Java object dependencies here.Call it via Springpackage com.java2s.common;

import org.springframework.context.ApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.java2s.output.OutputHelper;

public class App {

public static void main( String[] args ) { ApplicationContext context = new ClassPathXmlApplicationContext(new String[] {"Spring-Common.xml"});

OutputHelper output = (OutputHelper)context.getBean("OutputHelper"); output.print(); }

}

To switch Printer, we just need to change the Spring XML file for a different Printer. When Printer changed, we need to modify the Spring XML file only.

Front 54

Simple Spring code to run basic app context

Back 54

ApplicationContext context = new ClassPathXmlApplicationContext( "SpringBeans.xml");

OutputHelper output = (OutputHelper)context.getBean("outputHelper");

output.print();

}

Front 55

Spring property tag shortcut

Back 55

We can use shortcut property tag to fill value to Java bean properties in the following way.

The property tag can have a value attribute. We put our value there.

"p" schemaWe can even fill the properties when declaring the Java Bean in the bean tag.

In order to use the p schema we have to declare thexmlns:p="http://www.springframework.org/schema/p

Front 56

Spring import XML file

Back 56

Spring allows us to organize all Spring bean configuration files into a single XML file.

In order to host all configuration file we created a new Spring-All-Module.xml file, and import the other Spring bean files.

Put this file under project classpath.project-classpath/Spring-All-Module.xml

We can load a single xml file like this :

ApplicationContext context = new ClassPathXmlApplicationContext("Spring-All-Module.xml");

Front 57

what do you need in an XML config file to scan packages for beans?

Front 58

how to exclude classes from the scan?

Back 58

context:exclude-filter

Front 59

JDBC Example Code

Back 59

//STEP 1 Import classes

import java.sql.*

//STEP 2: Register JDBC driver Class.forName("com.mysql.jdbc.Driver");

//STEP 3: Open a connection System.out.println("Connecting to database...");

conn = DriverManager.getConnection(DB_URL,USER,PASS);

//STEP 4: Execute a query System.out.println("Creating statement..."); stmt = conn.createStatement();

String sql; sql = "SELECT id, first, last, age FROM Employees";

ResultSet rs = stmt.executeQuery(sql);

Front 60

JUnit Assert examples

Back 60

//check for equality

assertEquals("Abc", str);

//check for false condition

assertFalse(num > 6);

//check for not null value

assertNotNull(str);

Front 61

What's the result?

Back 61

public class Main{

public static void main(String[] argv){ StringBuilder sb = new StringBuilder(); sb.append("AAA").insert(1, "BB").insert(4, "CCCC"); System.out.println(sb);

}}

ABBACCCCA

Front 62

array to list

Back 62

List list = Arrays.asList(array);