Placeholder trick in Spring

Hello everyone! In the Spring Framework (I use Spring 2.5), we can use property placeholders in the spring xml-based configuration file. I wrote simple example that consist of four beans. Two of them are simple beans, one is a factory and one is a result bean that we want to get from factory bean.

<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd">

    <bean id=”simpleFactory” class=”c om.blogger.dooman87.SimpleFactory”>

        <constructor-arg value=”$ {com.blogger.dooman87.resultBeanName}”>

    </bean>

    <bean id="resultBean" factory-bean=”s impleFactory”/>

    <bean id="simpleBeanFirst"

        class="com.blogger.dooman87.SimpleBeanFirst"/>

    <bean id="simpleBeanSecond"

        class="com.blogger.dooman87.SimpleBeanSecond"/>

</beans>

In this case, we should write additional class com.blogger.dooman87.SimpleFactory, that would instantiate result by first constructor argument. This class we can extend from AbstractFactoryBean. But as well we are able to replace the factory! This simple trick you can see below:

<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd">

    <alias name="${com.blogger.dooman87.resultBeanName}" alias="resultBean"/>

    <bean id="simpleBeanFirst"

        class="com.blogger.dooman87.SimpleBeanFirst"/>

    <bean id="simpleBeanSecond"

        class="com.blogger.dooman87.SimpleBeanSecond"/>

</beans>

We created alias for result bean, where the name is a placeholder value. That's all. Hope this post was interesting or you.

Reading from InputStream

Lately I've faced a simple problem: I needed to read all bytes from the InputStream. I didn't know type of the InputStream, so, I've spent more then two hours solving this problem without any success. I didn't want to read each byte from the stream. All evening I could think only about this problem. Solution turned to be very simple! I found a sample in the JDK installation directory($JAVA_HOME/sample/nio/). JDK 1.5(and higher) is a good API to work with streams over channels. The source code to read all bytes from the InputStream is rather simple:

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.Reader;
import java.nio.ByteBuffer;
import java.nio.channels.Channels;
import java.nio.channels.ReadableByteChannel;

/**
 * @author Pokidov.Dmitry
 *         Date: 13.04.2009
 */
public class IOHelper {
 /*Block size that we want to read in one time.*/
 private static final int READ_BLOCK = 8192; 

 /*
  * Read all from stream, using nio.
  * @param is source stream.
  * @return result byte array that read from source
  * @throws IOException by {@code Channel.read()}
  */
 public static byte[] readToEnd(InputStream is) throws IOException {
  //create channel for input stream
  ReadableByteChannel bc = Channels.newChannel(is);
  ByteBuffer bb = ByteBuffer.allocate(READ_BLOCK);

  while (bc.read(bb) != -1) {
   bb = resizeBuffer(bb); //get new buffer for read
  }
  byte[] result = new byte[bb.position()];
  bb.position(0);
  bb.get(result);

  return result;
 }

 private static ByteBuffer resizeBuffer(ByteBuffer in) {
  ByteBuffer result = in;
  if (in.remaining() < READ_BLOCK) {
   //create new buffer
   result = ByteBuffer.allocate(in.capacity() * 2);
   //set limit to current position in buffer and set position to zero.
   in.flip();
   //put original buffer to new buffer
   result.put(in);
  }

  return result;
 }

Also I found an interesting book in which you can read about the nio package: get it here