How to set the default JDBC URL value in H2 console using spring boot

I have enable the H2 console in spring boot. However, when I open the console connection page the default url is the one staved in the H2 console history. How can i configure the project to populate the URL to be the same as spring.datasource.url on project start? Currently I set the url in the console manually but I would like to have it setup automatically by the project itself.

yaml:

spring:
  h2:
    console:
      enabled: true
      path: /admin/h2


  datasource:
    url: jdbc:h2:mem:foobar

update: I know that the last connection settings are saved to ~/.h2.server.properties but what I need is to set the properties from the starting application potentially, potentially switching between several of them

There is no hook provided to fill in settings.

The good news is that we can change that with a bit of code.

Current state

The Login screen is created in WebApp.index()

String[] settingNames = server.getSettingNames();
String setting = attributes.getProperty("setting");
if (setting == null && settingNames.length > 0) {
    setting = settingNames[0];
}
String combobox = getComboBox(settingNames, setting);
session.put("settingsList", combobox);
ConnectionInfo info = server.getSetting(setting);
if (info == null) {
    info = new ConnectionInfo();
}
session.put("setting", PageParser.escapeHtmlData(setting));
session.put("name", PageParser.escapeHtmlData(setting));
session.put("driver", PageParser.escapeHtmlData(info.driver));
session.put("url", PageParser.escapeHtmlData(info.url));
session.put("user", PageParser.escapeHtmlData(info.user));
return "index.jsp";

We want to tap into server.getSettingNames(), and precisely into server.getSettings() used underneath.

synchronized ArrayList<ConnectionInfo> getSettings() {
    ArrayList<ConnectionInfo> settings = new ArrayList<>();
    if (connInfoMap.size() == 0) {
        Properties prop = loadProperties();
        if (prop.size() == 0) {
            for (String gen : GENERIC) {
                ConnectionInfo info = new ConnectionInfo(gen);
                settings.add(info);
                updateSetting(info);
            }
        } else {
            for (int i = 0;; i++) {
                String data = prop.getProperty(Integer.toString(i));
                if (data == null) {
                    break;
                }
                ConnectionInfo info = new ConnectionInfo(data);
                settings.add(info);
                updateSetting(info);
            }
        }
    } else {
        settings.addAll(connInfoMap.values());
    }
    Collections.sort(settings);
    return settings;
}

The plan

• disable ServletRegistrationBean<WebServlet> created by H2ConsoleAutoConfiguration
• replace it with our config class with a subclass of WebServlet
• our CustomH2WebServlet will override init and register CustomH2WebServer (subclass of WebServer)
• in CustomH2WebServer we override getSettings() and we are done

The Code

@EnableConfigurationProperties({H2ConsoleProperties.class, DataSourceProperties.class})
@Configuration
public class H2Config {

    private final H2ConsoleProperties h2ConsoleProperties;

    private final DataSourceProperties dataSourceProperties;

    public H2Config(H2ConsoleProperties h2ConsoleProperties, DataSourceProperties dataSourceProperties) {
        this.h2ConsoleProperties = h2ConsoleProperties;
        this.dataSourceProperties = dataSourceProperties;
    }

    @Bean
    public ServletRegistrationBean<WebServlet> h2Console() {
        String path = this.h2ConsoleProperties.getPath();
        String urlMapping = path + (path.endsWith("/") ? "*" : "/*");
        ServletRegistrationBean<WebServlet> registration = new ServletRegistrationBean<>(
                new CustomH2WebServlet(this.dataSourceProperties.getUrl()), urlMapping);
        H2ConsoleProperties.Settings settings = this.h2ConsoleProperties.getSettings();
        if (settings.isTrace()) {
            registration.addInitParameter("trace", "");
        }
        if (settings.isWebAllowOthers()) {
            registration.addInitParameter("webAllowOthers", "");
        }
        return registration;
    }
}

package org.h2.server.web;

import javax.servlet.ServletConfig;
import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.Enumeration;

public class CustomH2WebServlet extends WebServlet {

    private final String dbUrl;

    public CustomH2WebServlet(String dbUrl) {
        this.dbUrl = dbUrl;
    }

    @Override
    public void init() {
        ServletConfig config = getServletConfig();
        Enumeration<?> en = config.getInitParameterNames();
        ArrayList<String> list = new ArrayList<>();
        while (en.hasMoreElements()) {
            String name = en.nextElement().toString();
            String value = config.getInitParameter(name);
            if (!name.startsWith("-")) {
                name = "-" + name;
            }
            list.add(name);
            if (value.length() > 0) {
                list.add(value);
            }
        }
        String[] args = list.toArray(new String[0]);
        WebServer server = new CustomH2WebServer(dbUrl);
        server.setAllowChunked(false);
        server.init(args);
        setServerWithReflection(this, server);
    }

    private static void setServerWithReflection(final WebServlet classInstance, final WebServer newValue) {
        try {
            final Field field = WebServlet.class.getDeclaredField("server");
            field.setAccessible(true);
            field.set(classInstance, newValue);
        }
        catch (SecurityException|NoSuchFieldException|IllegalArgumentException|IllegalAccessException ex) {
            throw new RuntimeException(ex);
        }
    }
}

package org.h2.server.web;

import java.util.ArrayList;
import java.util.Collections;

class CustomH2WebServer extends WebServer {

    private final String connectionInfo;

    CustomH2WebServer(String dbUrl) {

        this.connectionInfo = "Test H2 (Embedded)|org.h2.Driver|" +dbUrl+"|sa";
    }

    synchronized ArrayList<ConnectionInfo> getSettings() {
        ArrayList<ConnectionInfo> settings = new ArrayList<>();
        ConnectionInfo info = new ConnectionInfo(connectionInfo);
        settings.add(info);
        updateSetting(info);
        Collections.sort(settings);
        return settings;
    }
}

spring.h2.console.enabled=false
spring.datasource.url=jdbc:h2:mem:foobar

Everything went smoolthly, except of one private field that needed to be set via reflection.

The code provided works with H2 1.4.199