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Java example source code file (XmlBeanModule.java)

This example Java source code file (XmlBeanModule.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

beanbuilder, beanlistener, beanprovider, binder, class, element, list, method, missing, net, network, property, propertylistener, provider, reflection, runtimeexception, sax, string, util

The XmlBeanModule.java Java example source code

package example.xml;

import com.google.inject.Key;
import com.google.inject.Module;
import com.google.inject.Provider;
import com.google.inject.Binder;
import java.io.InputStreamReader;
import java.io.Reader;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Type;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
import org.xml.sax.Attributes;
import org.xml.sax.Locator;
import safesax.Element;
import safesax.ElementListener;
import safesax.Parsers;
import safesax.RootElement;
import safesax.StartElementListener;

public class XmlBeanModule implements Module {

  final URL xmlUrl;

  Locator locator;
  Binder originalBinder;
  BeanBuilder beanBuilder;

  public XmlBeanModule(URL xmlUrl) {
    this.xmlUrl = xmlUrl;
  }

  public void configure(Binder binder) {
    this.originalBinder = binder;

    try {
      RootElement beans = new RootElement("beans");
      locator = beans.getLocator();

      Element bean = beans.getChild("bean");
      bean.setElementListener(new BeanListener());

      Element property = bean.getChild("property");
      property.setStartElementListener(new PropertyListener());

      Reader in = new InputStreamReader(xmlUrl.openStream());
      Parsers.parse(in, beans.getContentHandler());
    }
    catch (Exception e) {
      originalBinder.addError(e);
    }
  }

  /** Handles "binding" elements. */
  class BeanListener implements ElementListener {

    public void start(final Attributes attributes) {
      Binder sourced = originalBinder.withSource(xmlSource());

      String typeString = attributes.getValue("type");

      // Make sure 'type' is present.
      if (typeString == null) {
        sourced.addError("Missing 'type' attribute.");
        return;
      }

      // Resolve 'type'.
      Class<?> type;
      try {
        type = Class.forName(typeString);
      }
      catch (ClassNotFoundException e) {
        sourced.addError(e);
        return;
      }

      // Look for a no-arg constructor.
      try {
        type.getConstructor();
      }
      catch (NoSuchMethodException e) {
        sourced.addError("%s doesn't have a no-arg constructor.");
        return;
      }

      // Create a bean builder for the given type.
      beanBuilder = new BeanBuilder(type);
    }

    public void end() {
      if (beanBuilder != null) {
        beanBuilder.build();
        beanBuilder = null;
      }
    }
  }

  /** Handles "property" elements. */
  class PropertyListener implements StartElementListener {

    public void start(final Attributes attributes) {
      Binder sourced = originalBinder.withSource(xmlSource());

      if (beanBuilder == null) {
        // We must have already run into an error.
        return;
      }

      // Check for 'name'.
      String name = attributes.getValue("name");
      if (name == null) {
        sourced.addError("Missing attribute name.");
        return;
      }

      Class<?> type = beanBuilder.type;

      // Find setter method for the given property name.
      String setterName = "set" + capitalize(name);
      Method setter = null;
      for (Method method : type.getMethods()) {
        if (method.getName().equals(setterName)) {
          setter = method;
          break;
        }
      }
      if (setter == null) {
        sourced.addError("%s.%s() not found.", type.getName(), setterName);
        return;
      }

      // Validate number of parameters.
      Type[] parameterTypes = setter.getGenericParameterTypes();
      if (parameterTypes.length != 1) {
        sourced.addError("%s.%s() must take one argument.",
            setterName, type.getName());
        return;
      }

      // Add property descriptor to builder.
      Provider<?> provider = sourced.getProvider(Key.get(parameterTypes[0]));
      beanBuilder.properties.add(
          new Property(setter, provider));
    }
  }

  static String capitalize(String s) {
    return Character.toUpperCase(s.charAt(0)) +
        s.substring(1);
  }

  static class Property {

    final Method setter;
    final Provider<?> provider;

    Property(Method setter, Provider<?> provider) {
      this.setter = setter;
      this.provider = provider;
    }

    void setOn(Object o) {
      try {
        setter.invoke(o, provider.get());
      }
      catch (IllegalAccessException e) {
        throw new RuntimeException(e);
      }
      catch (InvocationTargetException e) {
        throw new RuntimeException(e);
      }
    }
  }

  class BeanBuilder {
    
    final List<Property> properties = new ArrayList();
    final Class<?> type;

    BeanBuilder(Class<?> type) {
      this.type = type;
    }

    void build() {
      addBinding(type);
    }

    <T> void addBinding(Class type) {
      originalBinder.withSource(xmlSource())
          .bind(type).toProvider(new BeanProvider<T>(type, properties));
    }
  }

  static class BeanProvider<T> implements Provider {

    final Class<T> type;
    final List<Property> properties;

    BeanProvider(Class<T> type, List properties) {
      this.type = type;
      this.properties = properties;
    }

    public T get() {
      try {
        T t = type.newInstance();
        for (Property property : properties) {
          property.setOn(t);
        }
        return t;
      }
      catch (InstantiationException e) {
        throw new RuntimeException(e);
      }
      catch (IllegalAccessException e) {
        throw new RuntimeException(e);
      }
    }
  }

  Object xmlSource() {
    return xmlUrl + ":" + locator.getLineNumber();
  }
}

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