contact-base.json

{"fields":
  [{
    "type":"string",
    "name":"Firstname",
    "value":"Max"
  },
  {
    "type":"string",
    "name":"Lastname",
    "value":"Mustermann"
  },
  {
    "type":"string",
    "name":"Job Role",
    "value":"Chief Architect"
  },
  {
    "type":"string",
    "name":"Company",
    "value":"Codetrails UG"
  },
  {
    "type":"string",
    "name":"Street",
    "value":"Am Kirschbaum 7"
  }]
}

ContactEditorInput.java

package com.example.miniscout.client.editor;

import java.net.URI;

import org.eclipse.ui.internal.part.NullEditorInput;

public class ContactEditorInput extends NullEditorInput {

  private URI input;

  public ContactEditorInput(URI input) {
    this.input = input;
  }

  public URI getInput() {
    return input;
  }
}

DatabaseService.java

package com.example.miniscout.client.editor;

import static com.google.common.base.Charsets.UTF_8;

import java.io.File;
import java.io.IOException;
import java.net.URI;

import com.google.common.base.Throwables;
import com.google.common.io.CharStreams;
import com.google.common.io.Files;

public class DatabaseService {

  public static String load(URI uri) {
    try {
      return CharStreams.toString(Files.newReader(new File(uri), UTF_8));
    } catch (IOException e) {
      throw Throwables.propagate(e);
    }
  }

  public static void save(String data, URI uri) {
    try {
      if (uri.getScheme().equals("file")) {
        Files.write(data, new File(uri), UTF_8);
      } else
        throw new IllegalArgumentException("scheme " + uri + " not supported");
    } catch (IOException e) {
      throw Throwables.propagate(e);
    }
  }
}

Editor.java

package com.example.miniscout.client.editor;

import java.net.URI;

import org.eclipse.core.runtime.IProgressMonitor;
import org.eclipse.swt.SWT;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Text;
import org.eclipse.ui.IEditorInput;
import org.eclipse.ui.IEditorSite;
import org.eclipse.ui.PartInitException;
import org.eclipse.ui.part.EditorPart;

public class Editor extends EditorPart {

  private Text area;
  private String content;
  private URI input;

  @Override
  public void init(IEditorSite site, IEditorInput editorInput)
      throws PartInitException {
    setSite(site);
    setInput(editorInput);
    this.input = ((ContactEditorInput) editorInput).getInput();
    content = DatabaseService.load(this.input);
  }

  @Override
  public void createPartControl(Composite parent) {
    area = new Text(parent, SWT.MULTI);
    area.setText(content);
  }

  @Override
  public void doSave(IProgressMonitor monitor) {
    // not implemented yet
  }

  @Override
  public boolean isDirty() {
    // not implemented yet
    return false;
  }

  @Override
  public boolean isSaveAsAllowed() {
    return false;
  }

  @Override
  public void doSaveAs() {
  }

  @Override
  public void setFocus() {
  }
}

OpenHandler.java

package com.example.miniscout.client.editor;

import java.io.File;

import org.eclipse.core.commands.AbstractHandler;
import org.eclipse.core.commands.ExecutionEvent;
import org.eclipse.core.commands.ExecutionException;
import org.eclipse.swt.widgets.FileDialog;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.ui.IWorkbench;
import org.eclipse.ui.IWorkbenchWindow;
import org.eclipse.ui.PartInitException;
import org.eclipse.ui.PlatformUI;

public class OpenHandler extends AbstractHandler {

  @Override
  public Object execute(ExecutionEvent event) throws ExecutionException {
    IWorkbench wb = PlatformUI.getWorkbench();
    IWorkbenchWindow ww = wb.getActiveWorkbenchWindow();
    Shell shell = ww.getShell();
    FileDialog dialog = new FileDialog(shell);
    dialog.setFilterExtensions(new String[] { "*.json" });
    String file = dialog.open();
    if (file != null) {
      openEditor(ww, file);
    }
    return true;
  }

  private void openEditor(IWorkbenchWindow ww, final String file) {
    final File in = new File(file);
    try {
      ww.getActivePage().openEditor(new ContactEditorInput(in.toURI()),
          "com.example.miniscout.client.editor");
    } catch (PartInitException e) {
      e.printStackTrace();
    }
  }
}