Hi Martin,

Here's some sample code to upload a file to Content via the SOAP API and display the resulting object id - you can check its operation by browsing to https://na1.salesforce.com/<id> - replace na1 with your Salesforce instance.

package com.force.example.uploadcontent;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;

import com.sforce.soap.enterprise.Connector;
import com.sforce.soap.enterprise.EnterpriseConnection;
import com.sforce.soap.enterprise.Error;
import com.sforce.soap.enterprise.SaveResult;
import com.sforce.soap.enterprise.sobject.ContentVersion;
import com.sforce.ws.ConnectorConfig;

// Sample showing how to upload a file to Content
public class UploadContent {
    static final String USERNAME = "user@example.com";
    static final String PASSWORD = "********";
    static EnterpriseConnection connection;

    public static void main(String[] args) {
        if (args.length < 1) {
            System.err.println("Usage: UploadContent path [title] [description]");
            System.exit(-1);
        }

        String path = args[0];
        String title = (args.length > 1) ? args[1] : null;
        String description = (args.length > 2) ? args[2] : null;

        try {
            // Read the file
            byte[] data = loadFileAsByteArray(path);

            // Connect to Salesforce
            ConnectorConfig config = new ConnectorConfig();
            config.setUsername(USERNAME);
            config.setPassword(PASSWORD);
            // config.setTraceMessage(true);

            connection = Connector.newConnection(config);

            // Create an array of ContentVersion with a single member
            ContentVersion content = new ContentVersion();
            ContentVersion[] contentArray = { content };

            // Populate the ContentVersion fields
            content.setPathOnClient(path);
            if (title != null) {
                content.setTitle(title);
            }
            if (description != null) {
                content.setDescription(description);
            }
            content.setVersionData(data);

            // Upload the content to Salesforce
            SaveResult[] saveResults = connection.create(contentArray);

            // Check the returned results for any errors
            for (int i = 0; i < saveResults.length; i++) {
                if (saveResults[i].isSuccess()) {
                    System.out.println(i
                            + ". Successfully created record - Id: "
                            + saveResults[i].getId());
                } else {
                    Error[] errors = saveResults[i].getErrors();
                    for (int j = 0; j < errors.length; j++) {
                        System.out.println("ERROR creating record: "
                                + errors[j].getMessage());
                    }
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    // Simplest read of an entire file into a byte array
    // Will throw exceptions for file not found etc
    private static byte[] loadFileAsByteArray(String path) throws IOException {
        File file = new File(path);

        InputStream is = new FileInputStream(file);

        byte[] data = new byte[(int) file.length()];

        is.read(data);

        return data;
    }
}

The sample uses the Java WSC - you'll need to download wsc-20.jar and generate enterprise.jar as described in the article Introduction to the Force.com Web Services Connector

If you run the code in a dev org, you'll need to enable Content for the org and your user:

Setup > Customize > Salesforce CRM Content > Settings - turn on
Setup > Manage Users > Users > (select your user) - turn on 'Salesforce CRM Content User'

You can upload more than one file in the array, but bear in mind the maximum SOAP message size of 50MB.

Cheers,

Pat