waffel’s Weblog

Februar 27, 2013

testing REST interface with Spring 3.2 and a session scoped bean

Filed under: java,spring — Thomas Wabner @ 8:00 nachmittags
Tags: , , , , , , , , ,

There are some nice articles around the “spring 3.2 testing capabilities” like the spring documentation itself, this blog and this blog.

I wanted to not only test one request/response action against my REST interface. I wanted to simulate and test more of a conversation as it typical happens in the UI.

Following REST interface I wanted to create and test:

@RequestMapping("/customer")
public interface RESTCustomer {

@RequestMapping(
method = RequestMethod.POST)
@ResponseBody
Customer create(@RequestParam("firstname") final String firstname,
@RequestParam("lastname") final String lastname);

@RequestMapping(
method = RequestMethod.DELETE)
@ResponseStatus(HttpStatus.OK)
void delete(@RequestParam("id") final String... customerIds);

@RequestMapping(
produces = MediaType.APPLICATION_JSON_VALUE,
method = RequestMethod.GET)
@ResponseBody
Collection<Customer> getAll();

@RequestMapping(
value = "/update",
method = RequestMethod.POST)
@ResponseBody
Customer update(@RequestParam("id") final String id, @RequestParam("firstname") final String firstname);

}

Following test steps I had in mind, to test the create method:

  1. Get a list of all customers and remember the count
  2. Create a new customer
  3. Check, that the ID of the returning Customer was updated
  4. Get again a list of all customers
  5. Check the size of the customer list before and after creation … they should differ between one entry/li>

The new Spring Framework version 3.2 introduced some nice feature to do REST testing with minimal effort.

To test such conversion, you need beside the WebApplicationContext a MockHttpSession which has to be used between different mockMvc calls, on one test case.

The following base test structure is required:

@RunWith(SpringJUnit4ClassRunner.class)
@WebAppConfiguration
@ContextConfiguration(
  classes = {
    MyConfig.class,
  })
public class RESTCustomerTest {
  
@Autowired
  private WebApplicationContext wac;

  @Autowired
  MockHttpSession session;

  MockMvc mockMvc;

  ObjectMapper jsonObjectMapper;

  @Before
  public void setup() {
    mockMvc = MockMvcBuilders.webAppContextSetup(wac).build();
    jsonObjectMapper = new ObjectMapper();
  }

  @Test
  public void testCreate() throws Exception {
    ....
  }
}

Let assume, there is an implementation of the RESTCustomer service interface like this:


@Component
public class CustomerResource implements RESTCustomer {

  private final PlatformService service;

  @Autowired
  public CustomerResource(final PlatformService service) {
    this.service = service;
  }

  @Override
  public Customer create(final String firstname, final String lastname) {
    ...
    return service.createCustomer(firstname, lastname);
  }

  @Override
  public Collection<Customer> getAll() {
    ...
    return service.getAllCustomers();
  }

}

Assume also, that the autowired PlatformService is a Session scoped bean (somewhere configured inside the spring configuration).

Now our testing method can be like this:


  int countCustomers() throws Exception {
    final MvcResult mvcResult = mockMvc.perform(get("/customer").session(session).accept(MediaType.APPLICATION_JSON))
        .andReturn();
    final Collection<Customer> customers = getRawObjects(mvcResult);
    return customers.size();
  }

Collection<Customer> getRawObjects(final MvcResult mvcResult) throws Exception {
    return jsonObjectMapper.readValue(mvcResult.getResponse().getContentAsString(),
        new TypeReference<Collection<Customer>() {
        });
  }

Customer getRawObject(final MvcResult mvcResult) throws Exception {
    return jsonObjectMapper.readValue(mvcResult.getResponse().getContentAsString(),
        new TypeReference<Customer>() {
        });
  }

  @Test
  public void testCreate() throws Exception {
    // get default customer list and count
    final int originalCustomerSize = countCustomers();

    // create new customer
    final MvcResult mvcResult = mockMvc
        .perform(
            post("/customer/?firstname={firstname}&lastname={lastname}","testFirstname", "testLastName").session(session).accept(
                MediaType.APPLICATION_JSON)).andExpect(status().isOk()).andReturn();
    final Customer customerObject = getRawObject(mvcResult);
    assertNotNull("id of new customer should not empty", customerObject.get("id"));
    assertEquals("newly firstname should match", "testFirstname", customerObject.get("firstname");

    // again get list of all customers and check, if one more is available
    assertEquals("after new customer was created, the size should be one more", originalCustomerSize + 1, countCustomers());
  }

To get such conversation to work, you need to pass the session with .session(session) between the mockMvc calls. Else, every new mockMvc call creates a new session and your test fail.

REMEMBER: The trick is to pass the autowired MockHttpSession between the mock MVC requests.

März 28, 2011

Run eclipse RCP application via WebStart

Filed under: java — Thomas Wabner @ 7:07 nachmittags
Tags: , , , , , , , ,

The last days I need to create a small prototype to demonstrate how to start a eclipse RCP application via webstart. After reading many tutorials and tipps I have now a working setup which I want to share with you.

The main tutorial which I followed was the eclipse help itself. But there are some hidden points which are important to respect.

Lets start:

You need 4 Projects:

  • Eclipse RCP plugin
  • Feature for the plugin
  • Wrapping feature for webstart
  • entry or start JNLP file

At least you need an webserver which can deliver your files.

Create eclipse RCP plugin with a example RCP application provided by eclipse:

This plugin will provide the RCP application with a small demo UI. In a larger project you will normally have more than one plugin. But for demonstration proposed this would be enough.

  1. From the eclipse main menu, go to File > New > Project… (the New Project wizard opens), select Plugin-in Development > Plug-in Project
  2. Press Next > enter “org.test.webstart.demo.plugin” as Project name
  3. Press Next > change the Version to “0.1.0″
  4. Press Next > select RCP application with an view > press Finish

At this point you should have a small RCP “application” which can started from eclipse. Select the project root > select Run from the menu > select Run As > Eclipse Application. Now you should see the demo UI.

Next we need a Eclipse feature project which uses the plugin.

Create eclipse feature which contains the plugin and a reference to the eclipse rcp feature:

We need a feature which depends on the demo plugin and on the eclipse rcp feature. The dependency to the eclipse rcp feature is required to export later all required plugins and features for webstart, to run the complete rcp application.

  1. In the eclipse main menu go to File > New > Project… (the New Project Dialog opens), select Plug-in Development > Feature Project
  2. Press Next > enter “org.test.webstart.demo.feature” as project name > change the Version to “0.1.0″
  3. Press Next > select “org.test.webstart.demo.plugin” from plug-ins list > press Finish

The feature editor opens. Now you need to add the eclipse rcp feature as included feature. To do so select Included Feature tab in the feature editor > add “org.eclipse.rcp” as feature. Save and close the feature editor.

This feature contains now all you need to run your application as a full featured eclipse RCP application. Now we need another wrapping feature to get the Webstart launcher on board.

Create wrapping feature for webstart

This feature will be used to export all required JAR files with the eclipse java webstart exporter into a local filesystem.

  1. From the eclipse main menu select File > New > Project… (the New Project Dialog opens), select Plug-in Development > Feature Project
  2. Press Next > enter “org.test.webstart.demo.wrapperfeature” as project name > change the Version to “0.1.0″
  3. Press Finish. The feature editor opens.

Now we need a dependency to the equinox launcher plugin and include our own feature.

  1. In the feature editor select the Plug-ins tab > add “org.eclipse.equinox.launcher”.
  2. Select the Included Feature tab > add “org.test.webstart.demo.feature” > save the editor.
  3. From the project root select the eclipse main menu > select File > Export… > select Deployable Features (the export wizard opens)
  4. Press Select All
  5. In the Desitination tab select a directory where you want to export the JAR and JNLP files.
  6. In the Options tab only select Package as individual JAR archives. If you select Generate metadata repository nothing will be exported!
  7. In the JAR Signing tab fill in all fields with the information from your keystore. If you do not have an keystore you can create your own by follow these instructions.
  8. In the Java Webstart tab select Create JNLP manifests for the JAR archives > add the Site URL like http://localhost:8080/demoui-webstart > set 1.5+ for the JRE version > pess Finish

Now you should have in your destination folder a folder structure like
– features
– plugins

Under the features folder you should have some JNLP files. Because of an error in the eclipse exporter you need to adjust the JNLP files. For example the JNLP file of the feature looks like:

<?xml version="1.0" encoding="UTF-8"?>
<jnlp spec="1.0+" codebase="http://localhost:8080/demoui-webstart">
	<information>
		<title>Demo_rcp_feature</title>
		<offline-allowed/>
	</information>
	<security>
		<all-permissions/>
	</security>
	<component-desc/>
	<resources>
		<j2se version="1.5+" />
	</resources>
	<resources>
		<extension href="features/org.eclipse.rcp_3.5.2.R35x_v20100119-9SA0FxwFnoCU5XxWItFdXXb27BA6.jnlp" />
		<jar href="plugins/demo_rcp_0.1.0.201103241351.jar"/>
	</resources>
</jnlp

You need to change the tag and add the required vendor information. The resulting information tag should look like

	<information>
		<title>Demo_rcp_feature</title>	
		<vendor>Me</vendor>
		<offline-allowed/>
	</information

You need to do this for all JNLP files in the features folder!

Create start.jnlp file as the entry point for the web application

As a final step you need to create your entry JNLP file which is the starting point of your webstart application. Here is an example for start.jnlp:

<?xml version="1.0" encoding="UTF-8"?>
<jnlp 
    spec="1.0+" 
    codebase="http://localhost:8080/demoui-webstart" 
    href="start.jnlp"> 
  <information>
    <!-- user readable name of the application -->
    <title> Demo UI Application </title>  
    <!-- vendor name -->
    <vendor>Me</vendor>
    <!-- vendor homepage --> 
    <homepage href="http://www.me.org" /> 
    <!-- product description -->
    <description>description</description> 
    <offline-allowed/>
  </information>
 
  <!--request all permissions from the application. This does not change-->
  <security>
    <all-permissions/>
  </security>
 
  <!-- The name of the main class to execute. This does not change-->
  <application-desc main-class="org.eclipse.equinox.launcher.WebStartMain">
    <argument>-nosplash</argument>
  </application-desc>
 
  <resources>
    <!-- Reference to the launcher jar. The version segment must be updated to the version being used-->
    <jar href="plugins/org.eclipse.equinox.launcher_1.0.201.R35x_v20090715.jar"/>
 
    <!-- Reference to all the plugins and features constituting the application -->
    <!-- Here we are referring to the wrapper feature since it transitively refers to all the other plug-ins  necessary -->
    <extension 
        name="Wrapper feature"
        href="features/
org.test.webstart.demo.wrapperfeature_0.1.0.jnlp"/>
 
    <!-- Information usually specified in the config.ini -->
    <property 
        name="osgi.instance.area" 
        value="@user.home/Application Data/demoui-rcp"/>
    <property 
        name="osgi.configuration.area" 
        value="@user.home/Application Data/demoui-rcp"/>
    <!-- The id of the product to run, like found in the overview page of the product editor -->
    <property 
        name="eclipse.application" 
        value="org.demo.webstart.plugin.application"/>
  </resources>

  <!-- Indicate on a platform basis which JRE to use --> 
  <resources os="Windows">
    <j2se version="1.5+"/>
  </resources>
  <resources os="Linux">
    <j2se version="1.5+"/>
  </resources>
</jnlp>

Some remarks according the main JNLP file:

You need to adjust (or take care) of the lines 04, 30, 36, 48.

Line 04 defines the codebase. Every time you want to deploy you application on an websever you need to adjust the codebase (in every JNLP file in your project!) to the web application location.

Line 30 depends on you eclipse distribution (I have used eclipse 3.5 with some updates). You have to check the right version in your plugins folder and update the start.jnlp file.

Line 36 defines the starting feature JNLP file. This file itself refers to the other JNLP files in the features folder (which is automatically done from the eclipse exporter). You need to adjust this line if your project name differs from this example.

Line 48 defines the entry point to your application. This is the application ID from the example plugin. You can find the ID if you open the plugin editor of your example plugin. To do so open your example plugin and open the plugin.xml file. Under the tab Overview you can find the ID: “org.demo.webstart.plugin”. Now you also need to open the tab Extensions. Under the Extensions Details you can find the ID of your application. The complete application ID which you need to refer in the JNLP file is then “org.demo.webstart.plugin.application”.

If you now put the main JNLP file and the plugins + features folders under an webserver which delivers the files from http://localhost:8080/demoui-webstart/ you can see your test application. You should have following structure:

- start.jnlp
|– features
|– plugins

Simple click following link: http://localhost:8080/demoui-webstart/start.jnlp

Hint:
A small problem over which I stumbled while developing the example application:

If you start the application and you get from webstart an exception that plugin with *WTP* are not found, you can have a look into the JNLP files in the features folder. Some of these files define resources which are not exported by the eclipse webstart exporter. I have simple removed these resources from the JNLP files and it works.

Update:
I have created a Github repository with some code examples. You may clone my repo or send me patches with corrections.

Additional update:
I have now finished my github example and pushed also a complete working example. If you want to see how it works you can pull the https://github.com/waffel/Wordpress-examples/tree/master/org.waffel.worpress.demo.webstart.result project. With the help of maven you can simple start the application via

mvn jetty:run

This launches the jetty webserver and you can hit your browser to http://localhost:8080/demoui-webstart/start.jnlp

I have done all the mentioned steps from this blog for myself with a eclipse 3.7.

September 7, 2010

Columba – Java based EMail-Client honoured by big IT Magazin in Germany

Filed under: java,software — Thomas Wabner @ 6:27 nachmittags
Tags: , , , ,

As anybody knows I’am a Co-developer for the last years for a Java based EMail client called Columba. Now the program was honoured by the big german IT magazin Heise.

The last moths, there are no more many code changes in the project and I can say the project is dead (from the developer point of view). I have learned many about open source programming, Java coding and got new friends in this project. It was very funny to work on this EMail client!

Now we got after many years good feedback for our work and it is nice to see that the project still have users which are like this kind of EMail client.

August 21, 2009

use your own variable in eclipse code templates

Filed under: java — Thomas Wabner @ 2:08 nachmittags
Tags: , , ,

On my work we develop eclipse plugins and want to add the current bundle id and bundle version to the since field for class comments. There are not much examples around this problem (we have searched google and eclipse help) so let me explain how you can achive this.

For example we want to define follow code template:

/**
 * @author ${user}
 *
 * ${tags}
 * @since ${bundleId} ${bundleVersion}
 */

The bundleId and bundleVersion variable are not provided by the standard code template variables. Now we have to find out how we can achive this problem.

First of all you need to develop your own eclipse plugin which should provide such feature. The new plugin requires follow dependencies:

  • org.eclipse.core.resources;bundle-version=”3.5.0″,
  • org.eclipse.ui;bundle-version=”3.5.0″,
  • org.eclipse.jface.text;bundle-version=”3.5.0″,
  • org.eclipse.jdt.core;bundle-version=”3.5.0″,
  • org.eclipse.jdt.ui;bundle-version=”3.5.0″,
  • org.eclipse.core.runtime;bundle-version=”3.5.0″,
  • org.eclipse.pde.core;bundle-version=”3.5.0″

The PDE dependency is needed to get the current bundle id and the bundle version. If you need other features (for example a maven project version) you have depend on other plugins. But in this example I’ll show you how to add bundle id and bundle version as extra variable for the eclipse code templates.

Next you have to create a extention to register your own variable resolver at startup. The variable resolvers are the heart of the plugin because they providing new variables for the code templates to be used and resolving the content if you use the code template.

plugin.xml:

< ?xml version="1.0" encoding="UTF-8"?>
< ?eclipse version="3.4"?>
<plugin>
   <extension point="org.eclipse.ui.startup">
      <startup class="yourplugin.eclipse.javadoc.internal.RegisterResolvers">
      </startup>
   </extension>
</plugin>

The RegisterResolvers class implements the IStartup interface from eclipse. This class registers the variable resolvers to the code template context. This is required to have the variables available in the code templates from eclipse.

RegisterResolver:

/**
   * 
   * {@inheritDoc}
   * 
   * @see IStartup#earlyStartup()
   * 
   */
  public void earlyStartup() {
    // check if plug-in org.eclipse.jdt.ui is already active
    final Bundle bundle = Platform.getBundle(PLUGIN_ID);
    if (bundle != null && bundle.getState() == Bundle.ACTIVE) {
      // register resolvers
      registerResolvers();
    } else {
      // register listener to get informed, when plug-in becomes active
      final BundleContext bundleContext = Activator.getDefault().getBundle().getBundleContext();
      bundleContext.addBundleListener(new BundleListener() {
        public void bundleChanged(final BundleEvent pEvent) {
          final Bundle bundle2 = pEvent.getBundle();
          if (!bundle2.getSymbolicName().equals(PLUGIN_ID)) {
            return;
          }
          if (bundle2.getState() == Bundle.ACTIVE) {
            registerResolvers();
            bundleContext.removeBundleListener(this);
          }
        }
      });
    }
  }

/**
   * 
   * Internal method to register resolvers with all context types.
   * 
   */
  private void registerResolvers() {
    final ContextTypeRegistry codeTemplateContextRegistry = JavaPlugin.getDefault().getCodeTemplateContextRegistry();
    final Iterator ctIter = codeTemplateContextRegistry.contextTypes();
    while (ctIter.hasNext()) {
      final TemplateContextType contextType = (TemplateContextType) ctIter.next();
      contextType.addResolver(new BundleIdResolver());
      contextType.addResolver(new BundleVersionResolver());

    }
  }

The bundleIdResolver extends the TemplateVariableResolver and defines (in the default constructor) the variable name which can be used later in the code template, a description and overrides the resolve method.

The resolve method checks if the current project is a plugin project and if so returns the bundle id from the project.

public class BundleIdResolver extends TemplateVariableResolver {
  /**
   * 
   * Constructs a new <code>BundleIdResolver</code>.
   * 
   */
  public BundleIdResolver() {
    super("bundleId", "id of the bundle containing the current compilation unit");
  }

  /**
   * 
   * {@inheritDoc}
   * 
   * @see TemplateVariableResolver#resolve(org.eclipse.jface.text.templates.TemplateContext)
   * 
   */
  @Override
  protected String resolve(final TemplateContext pContext) {
    final CodeTemplateContext context = (CodeTemplateContext) pContext;
    final IPluginModelBase pluginModelBase = PluginRegistry.findModel(context.getJavaProject().getProject());
    if (pluginModelBase == null) {
      return null;
    }
    return pluginModelBase.getBundleDescription().getSymbolicName();
  }
}

Now you can come up with the question why not you can use the standard eclipse extention point mechanism and create your own context.

Well, we want to extend the java context but the current eclipse implementation doe’s not provide such functionality. For sure if you want to have your own context you can do this with the standard extention point mechanism (as the Ant example). There is a small example about the eclipse editor templates.

Thanks to my colleague Marco Lehmann for the complete solution.

November 28, 2008

how to use EL from java in a JSF 1.2 environment

Filed under: java,JSF,software — Thomas Wabner @ 9:47 nachmittags
Tags: , , ,

There are not much examples, how to use a ELExpression from your java code. The most examples I found, are focussing on “implement your own ELResolver”. The best documentation comes from SUN in form of tutorials and package/javadoc.

Now I will provide some tips how to deal with EL expressions from java. I have tested and implemented this in a JSF 1.2 web application, where I have access to the FacesContext.

In JSF 1.2 you have access to expression factory:

// get application from faces context
Application app = FacesContext.getInstance().getApplication();
ExpressionFactory exprFactory = app.getExpressionFactory();

Now you can use the expression factory to get a MethodExpression or ValueExpression. In my projects we need very often ValueExpressions.

But first you need also an ELContext. There are many implementations available of such context (for JSP, Faces and so on) and enough documentation how to create your own context.
You can access such context again from the faces context:

// getting the ELContext from faces context
ELContext elContext = FacesContext.getInstance().getELContext();
// creating value expression with the help of the expression factory and the ELContext
ValueExpression valExpr = exprFactory.createValueExpression(elContext, "#{devBean.devMode}", Boolean.class);

In this example I will use the boolean value from a “devBean” to work later with this value. Of course, you can inject the value expression, required class type and so on.
The last needed thing is to assign the value to a local variable:

Boolean developmentMode = (Boolean) valExpr.getValue(elContext);

Thats it!

September 9, 2008

expanding richfaces tree on datamodel changes

Filed under: java,JSF — Thomas Wabner @ 2:19 nachmittags
Tags: , , ,

Sometimes you will select a tree node in a richfaces tree, triggered by your datamodel. There are several hints how to do this with a tree state advisor, but I have found another way to do this.

My main problem was, that I do not have a relation between my datamodel and the richfaces UITree components (nodes). This problem was introduced because I use the recursiveTreeAdaptor. I have not found a way to get a TreeRowData object from the UITree for my datamodel object.

I have searched in the richfaces implementation, if there is another way to work with my datamodel which have to expand the tree, if the datamodel is changed.

Lets clearify what I want to do: I have a datamodel with some root nodes and “normal” nodes in a tree like structure. I have also (in my TreeManager) a parameter which holds a selectedNode. A node can selected from the UI (the user clicks on a tree node and causes a node selection event) or from my datamodel, which calls a method in the TreeManager to select a specific tree node.

The tree manager contains a method to select a specific node like this:

public void select(final Node nextStepNode) {
  this.selectedNode = nextStepNode;

}

To expand the tree to the selected node, I have changed to select method:

public void select(final Node nextStepNode) {
  this.selectedNode = nextStepNode;
  try {
      // walk over the tree which expands the tree and uses a complete tree
      // range
      tree.walk(FacesContext.getCurrentInstance(), expandingDataVisitor, new CompleteTreeRange(), null, null);
    } catch (final IOException e) {
      if (LOG.isErrorEnabled()) {
        LOG.error(String.format("problem %s", e.getMessage()));
      }
    }
}

The tree walk method walks over the tree using my own data visitor and tree range. The tree range implementation tolds the tree to walk also over hidden nodes. You remember? The tree should expand all nodes to the selected node, also if the selected node is hidden.

The tree range implementation looks like:

public class CompleteTreeRange implements TreeRange {

  /**
   * {@inheritDoc}
   */
  @SuppressWarnings("unchecked")
  public boolean processChildren(final TreeRowKey rowKey) {
    return true;
  }

  /**
   * {@inheritDoc}
   */
  @SuppressWarnings("unchecked")
  public boolean processNode(final TreeRowKey rowKey) {
    return true;
  }

Now comes the hard stuff on my solution, the expandingDataVisitor:

public class ExpandingDataVisitor implements DataVisitor {
  public void process(final FacesContext theContext, final Object theRowKey, final Object theArgument)
      throws IOException {
    if (selectedNode.equals(tree.getRowData(theRowKey))) {
      tree.queueNodeExpand((TreeRowKey) tree.getParentRowKey(theRowKey));
    }
}

You can queue node expanding with a tree rowKey to the node, which you want to expand. You don’t need to queue all nodes on the path. The queueNodeExpand method works fine with one rowkey. The row describes itself the complete path to the node. If you use standard jsf ID’s, a possible treeRowKey looks like “jsp123:jsp124:jsp125″ wich is the complete path to your node (row key).

You have to know, that you don’t want expand the selected node (this is in most cases a leafe). You want to expand the tree to the parent of the selected node.

Juni 13, 2008

getting node data from rich tree on user selection

Filed under: java,JSF,software — Thomas Wabner @ 3:33 nachmittags
Tags: , ,

I have had the problem to get node data from a richfaces tree, if the user selects a node. I have used a recursive tree adapter:

<rich:tree switchType="server"
           stateAdvisor="#{treeStateAdvisor}"
           nodeSelectListener="#{treeMgrt.onSelect}">
                 
   <rich:recursiveTreeNodesAdaptor roots="#{treeMgrt.roots}" var="item" nodes=" {item.nodes}">

     <rich:treeNode>
         <h:outputText value="#{item}"/>
     </rich:treeNode> 
          
  </rich:recursiveTreeNodesAdaptor>
</rich:tree>  

The method in my tree manager onSelect(…) looks like this:

public void onSelect(final NodeSelectedEvent event) {
  final UITree theTree = this.getTree(event);
  if (null == theTree) {
    return;
  }
  final Object rowKey = theTree.getRowKey();
  // this works better
  final Object rowData = theTree.getRowData(rowKey);
  if (rowData instanceof ProductNode) {
    this.selectedNode = (ProductNode) rowData;
  }
}

Normally you can use theTree.getTreeNode(); but with a recursive tree model which method returns alway null. Instead of this I have used the getRowData() method which works for me.
I have filed a bug for richfaces. Hope the problem becomes shortly a solution.

Oktober 9, 2007

Fast stream copy using java.nio channels

Filed under: java,nio,software — Thomas Wabner @ 11:21 vormittags
Tags: , , ,

Many times I was asked how to copy fast and simple an input stream to an output stream. I have found a nice solution on koders.com . A programmer named Mr. Hitchens has contributed this code.

Here are my utility method which makes the real fast copy stuff:

public final class ChannelTools {
  public static void fastChannelCopy(final ReadableByteChannel src, final WritableByteChannel dest) throws IOException {
    final ByteBuffer buffer = ByteBuffer.allocateDirect(16 * 1024);
    while (src.read(buffer) != -1) {
      // prepare the buffer to be drained
      buffer.flip();
      // write to the channel, may block
      dest.write(buffer);
      // If partial transfer, shift remainder down
      // If buffer is empty, same as doing clear()
      buffer.compact();
    }
    // EOF will leave buffer in fill state
    buffer.flip();
    // make sure the buffer is fully drained.
    while (buffer.hasRemaining()) {
      dest.write(buffer);
    }
  }
}

And how you can use this method to copy an input stream into an output stream? Here comes the answer:


// allocate the stream ... only for example
final InputStream input = new FileInputStream(inputFile);
final OutputStream output = new FileOutputStream(outputFile);
// get an channel from the stream
final ReadableByteChannel inputChannel = Channels.newChannel(input);
final WriteableByteChannel outputChannel = Channels.newChannel(output);
// copy the channels
ChannelTools.fastChannelCopy(inputChannel, outputChannel);
// closing the channels
inputChannel.close();
outputChannel.close()

The Rubric Theme. Erstelle eine kostenlose Website oder einen kostenlosen Blog – auf WordPress.com!.

Folgen

Erhalte jeden neuen Beitrag in deinen Posteingang.

Schließe dich 28 Followern an