I m having hard time to decide between the following two implementations. I want to cache the javax.xml.parsers.DocumentBuilder object, per thread. My main concern is runtime performance - Hench I would be happy to avoid as much GC as possible. Memory is not an issue.

我写了两个POC执行书,并乐于听取社区项目/CONS关于每个项目的发言。

感谢这些帮助。

Option #1 - WeakHashMap

import java.io.IOException;
import java.io.StringReader;
import java.util.WeakHashMap;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

import org.w3c.dom.Document;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;


public class DocumentBuilder_WeakHashMap {
    private static final DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    private static final WeakHashMap<Thread, DocumentBuilder> CACHE = new WeakHashMap<Thread, DocumentBuilder>();

    public static Document documentFromXMLString(String xml) throws SAXException, IOException, ParserConfigurationException {
        DocumentBuilder builder = CACHE.get(Thread.currentThread());
        if(builder == null) {
            builder = factory.newDocumentBuilder();
            CACHE.put(Thread.currentThread(), builder);
        }

        return builder.parse(new InputSource(new StringReader(xml)));
    }

}

Option #2 - ThreadLocal

import java.io.IOException;
import java.io.StringReader;
import java.lang.ref.WeakReference;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

import org.w3c.dom.Document;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;


public class DocumentBuilder_ThreadLocal {
    private static final DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    private static final ThreadLocal<WeakReference<DocumentBuilder>> CACHE = 
        new ThreadLocal<WeakReference<DocumentBuilder>>() {
            @Override 
            protected WeakReference<DocumentBuilder> initialValue() {
                try {
                    return new WeakReference<DocumentBuilder>(factory.newDocumentBuilder());
                } catch (Exception e) {
                    throw new RuntimeException(e);
                }
            }
        };

    public static Document documentFromXMLString(String xml) throws ParserConfigurationException, SAXException, IOException {
        WeakReference<DocumentBuilder> builderWeakReference = CACHE.get();
        DocumentBuilder builder = builderWeakReference.get();

        if(builder == null) {
            builder = factory.newDocumentBuilder();
            CACHE.set(new WeakReference<DocumentBuilder>(builder));
        }

        return builder.parse(new InputSource(new StringReader(xml)));
    }
}

两者都是一样的(将FromXMLString(FromXMLString)文件传给外部世界),以便你们能够使用?

Thank you, Maxim.