Settings 4 Spring

Did you ever used about:config in Firefox or chrome://flags in Chrome and thought to yourself: "Gee, what a lovely idea. Why my app doesn't have that?" Well that is what this project is about. Configure your app using Spring but store your application constants in persistent external store.

Usage

Start by creating db table:

-- Oracle, H2 syntax:
CREATE TABLE SETTINGS(
    PREFERENCENAME VARCHAR2(100) NOT NULL,      -- preference name
    VALUE VARCHAR2(1000),                       -- current value of preferencec
    DEFAULTVALUE VARCHAR2(1000),                -- default value
    TYPE VARCHAR2(100) NOT NULL,                -- Datatype: Boolean [bool, boolean, java.lang.Boolean], integer [int, integer, java.lang.Integer], long [long, java.lang.Long], string [string, java.lang.String]
    STATUS VARCHAR2(50) NOT NULL,               -- status: DEFAULT | USER SET
    DESCRIPTION VARCHAR2(500)                   -- preference description

    CONSTRAINT setting_pk PRIMARY KEY(PREFERENCENAME)
);

-- MySQL, Maria, PostgreSQL:
CREATE TABLE IF NOT EXISTS SETTINGS(
    PREFERENCENAME VARCHAR(100) NOT NULL, VALUE VARCHAR(1000), DEFAULTVALUE VARCHAR(1000), TYPE VARCHAR(100) NOT NULL, STATUS VARCHAR(50) NOT NULL, DESCRIPTION VARCHAR(500),
    PRIMARY KEY(PREFERENCENAME)
);

Add settings dependency to your project:

<dependency>
    <groupId>hr.ispcard.tools</groupId>
    <artifactId>Settings</artifactId>
    <version>1.4.3</version>
</dependency>

Add spring beans in your context:

<bean id="settingsDao" class="mt.tools.spring.settings.H2SettingsDao"
      p:tablename="SETTINGS"
      p:jdbcTemplate-ref="..." />

<bean id="settingFactoryBean" class="hr.ispcard.tools.settings.SettingFactoryBean" abstract="true"
      p:description="Missing description for this propert"
      p:settingsDao-ref="settingsDao" />

And you are ready to go. Use settingsFactoryBean to init any app preference:

<bean id="aStringValue" p:type="java.lang.String" parent="settingFactoryBean"
      p:description="This is an example of a text value"
      p:defaultValue="Example Value" />

<bean id="aIntValue" p:type="java.lang.Integer" parent="settingFactoryBean"
      p:description="And this is a integer value"
      p:defaultValue="5" />

<bean id="usageExample" class="myapp.ExampleService"
      p:textValUsage-ref="aStringValue"
      p:intValUsage-ref="aIntValue" />

Each variable is a normal spring bean in a app context, instantiated by SettingsFactoryBean. While variable is instantiated, the SettingsFactoryBean will try to match its id to a PREFERENCENAME in a table. If a matching row is found a value from VALUE column in table will be loaded. If a matching row was not found a row will be inserted in a table, with a VALUE column set to defaultValue property.

Multitenacy

TBD - Explain prefix mechanism

Using multiple tables

TBD - Use multiple tables to differenate settings

Using overrides

TBD - Use embeded properties to override default value

Special cases

TBD

Explain converters. Explain how to load list, map, and set. Write custom converter.