In my application.yml file, I want to define a list of rules.
rules:
- name: abc
value: something
- name: edf
value: something
Then I want to define a service like this
#Service
public class MyService {
public MyService(#Value("${rules}") List<Rule> rules) {
}
}
For the Rule pojo, it's like this.
public class Rule {
public String name, value;
}
Currently, I'm facing these errors.
If I leave rules empty, it throws can't convert String to List<Rule>
rules: []
If I keep the values, it throws could not resolve placeholder 'rules'
I really don't know what I'm doing wrong here.
From Spring docs, I found this.
Using the #Value("${property}") annotation to inject configuration
properties can sometimes be cumbersome, especially if you are working
with multiple properties or your data is hierarchical in nature.
Spring Boot provides an alternative method of working with properties
that lets strongly typed beans govern and validate the configuration
of your application
Link: https://docs.spring.io/spring-boot/docs/current/reference/html/boot-features-external-config.html#boot-features-external-config-typesafe-configuration-properties
At the end, I have to introduce another class.
#Configuration
#ConfigurationProperties(prefix="rules")
public class Rules {
public List<Rule> list;
}
Then I autowire it in MyService.
Related
#Configuration
public class MyWebMvcConfigurationSupport extends WebMvcConfigurationSupport {
#Override
public FormattingConversionService mvcConversionService() {
FormattingConversionService f = super.mvcConversionService();
f.addFormatter(new DateFormatter("yyyy-MM-dd"));
return f;
}
}
#RestController
public class TestController {
#GetMapping
public Date test(Date date) {
return date;
}
}
When we access http://localhost:8080?date=2021-09-04, the argument type is converted through the DateFormatter's parse method, which relies on the SpringMVC framework to do the conversion. I wonder if the print method can also be invoked through the framework to return a string.
Do we need to manually invoke the print method, for example
#RestController
public class TestController {
#Resource
private FormattingConversionService conversionService;
#GetMapping
public String test(Date date) {
return conversionService.convert(date, String.class);
}
}
Inside the controller
You could use a class extending java.text.Format like SimpleDateFormatin your controller:
#RestController
public class TestController {
private static final SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
#GetMapping
public String test(Date date) {
return dateFormat.format(date);
}
}
At application level
Use DateTimeFormatterRegistrar to register your formats, like described in this tutorial.
Then you can register this set of formatters at Spring's FormattingConversionService.
Using Jackson
However if you would like to work with JSON or XML you should consider using FasterXML's Jackson. See similar question:
Spring 3.2 Date time format
This is the interface representing the environment in which the current application is running. It models two key aspects of the application environment: profiles and properties. The methods related to property access are exposed via the PropertyResolver superinterface.
A profile is a named, logical group of bean definitions to be registered with the container only if the given profile is active. Beans may be assigned to a profile whether defined in XML or via annotations; see the spring-beans 3.1 schema or the #Profile annotation for syntax details. The role of the Environment object with relation to profiles is in determining which profiles (if any) are currently active, and which profiles (if any) should be active by default.
Properties play an important role in almost all applications, and may originate from a variety of sources: properties files, JVM system properties, system environment variables, JNDI, servlet context parameters, ad-hoc Properties objects, Maps, and so on. The role of the environment object with relation to properties is to provide the user with a convenient service interface for configuring property sources and resolving properties from them.
Beans managed within an ApplicationContext may register to be EnvironmentAware or #Inject the Environment in order to query profile state or resolve properties directly.
In most cases, however, application-level beans should not need to interact with the Environment directly but instead may have to have ${...} property values replaced by a property placeholder configurer such as PropertySourcesPlaceholderConfigurer, which itself is EnvironmentAware and as of Spring 3.1 is registered by default when using context:property-placeholder/.
Configuration of the environment object must be done through the ConfigurableEnvironment interface, returned from all AbstractApplicationContext subclass getEnvironment() methods. See ConfigurableEnvironment Javadoc for usage examples demonstrating manipulation of property sources prior to application context refresh().
I am having two implementations of my component.
public interface MyComponent {
}
imple1
#Component("impCompf")
#Lazy
#RequestScope
public class ImpComp1 implements MyComponent {
}
imple2
#Component("impComps")
#Lazy
#RequestScope
public class ImpComp2 implements MyComponent {
}
What I did so far is to create two conditions like so:
imple1
public class FirstCondition implements Condition {
#Override
public boolean matches(ConditionContext arg0, AnnotatedTypeMetadata arg1) {
return staticVariable.contains("impCompf");
}
}
Same goes for imple2
and define a configuration class
#Configuration
public class MyConfiguration {
#Bean
#Conditional(FirstCondition .class)
#Primary
public MyComponent getComp1() {
return new ImpComp1();
}
public static String staticVariable= "impCompf";
and in My main controller:
#RequestMapping(value="api/{co}", method=RequestMethod.POST)
public ResponseEntity<Modelx> postSe(#PathVariable("co") String co) {
if(co.contains("impCompf"))
staticVariable = "impCompf";
else (co.contains("impComps"))
staticVariable = "impComps";
What I want: for every http request I want to load proper implementation
But however what I am getting is the implementation defined first in the static variable.
If is there another elegant and better way, i'd like to know about it.
I think there is some confusion here about the purpose of the conditions. These aren't being used at the time your requests arrive to autowire the candidate bean into your controller. These are being used when the application is started to configure the application context based on the environment and classpath etc...
There is no need for the conditional classes that you have created. This is defining the configuration of the beans when the context starts and not on a per request basis at runtime.
The use of the static variable is also problematic is a scenario with one or more concurrent requests or in a case where multiple threads may observe different values unless some other mechanism in the java memory model is being used (such as volatile or establishing a happens before relationship, e.g. with sychnronized)
There are a number of ways to do what you appear to be trying to achieve. Since ultimately, you appear to be using a path parameter supplied by a client to determine which service you want to invoke you could use a classic factory pattern to return the correct interface implementation based on the string input programmatically.
Alternatively you could create two distinct controller methods which are distinguished by a query parameter or endpoint name or path match etc. You could then have the appropriate service injected by a qualified bean name
Although perhaps generally recommended, you could also inject an application context instance and search the it looking for the relevant bean by name or class: https://brunozambiazi.wordpress.com/2016/01/16/getting-spring-beans-programmatically/ - although This is more cumbersome and you'd need to handle things like org.springframework.beans.factory.NoSuchBeanDefinitionException or casting in some cases - best avoided in favour of one of the other methods.
I build a Spring-Boot application that accesses a Database and extracts data from it. Everything is working fine, but I want to configure the table names from an external .properties file.
like:
#Entity
#Table(name = "${fleet.table.name}")
public class Fleet {
...
}
I tried to find something but I didn't.
You can access external properties with the #Value("...") annotation.
So my question is: Is there any way I can configure the table names? Or can I change/intercept the query that is sent by hibernate?
Solution:
Ok, hibernate 5 works with the PhysicalNamingStrategy. So I created my own PhysicalNamingStrategy.
#Configuration
public class TableNameConfig{
#Value("${fleet.table.name}")
private String fleetTableName;
#Value("${visits.table.name}")
private String visitsTableName;
#Value("${route.table.name}")
private String routeTableName;
#Bean
public PhysicalNamingStrategyStandardImpl physicalNamingStrategyStandard(){
return new PhysicalNamingImpl();
}
class PhysicalNamingImpl extends PhysicalNamingStrategyStandardImpl {
#Override
public Identifier toPhysicalTableName(Identifier name, JdbcEnvironment context) {
switch (name.getText()) {
case "Fleet":
return new Identifier(fleetTableName, name.isQuoted());
case "Visits":
return new Identifier(visitsTableName, name.isQuoted());
case "Result":
return new Identifier(routeTableName, name.isQuoted());
default:
return super.toPhysicalTableName(name, context);
}
}
}
}
Also, this Stackoverflow article over NamingStrategy gave me the idea.
Table names are really coming from hibernate itself via its strategy interfaces. Boot configures this as SpringNamingStrategy and there were some changes in Boot 2.x how things can be customised. Worth to read gh-1525 where these changes were made. Configure Hibernate Naming Strategy has some more info.
There were some ideas to add some custom properties to configure SpringNamingStrategy but we went with allowing easier customisation of a whole strategy beans as that allows users to to whatever they need to do.
AFAIK, there's no direct way to do config like you asked but I'd assume that if you create your own strategy you can then auto-wire you own properties to there. As in those customised strategy interfaces you will see the entity name, you could reserve a keyspace in boot's configuration properties to this and match entity names.
mytables.naming.fleet.name=foobar
mytables.naming.othertable.name=xxx
Your configuration properties would take mytables and within that naming would be a Map. Then in your custom strategy it would simply be by checking from mapping table if you defined a custom name.
Spring boot solution:
Create below class
#Configuration
public class CustomPhysicalNamingStrategy extends SpringPhysicalNamingStrategy{
#Value("${table.name}")
private String tableName;
#Override
public Identifier toPhysicalTableName(final Identifier identifier, final JdbcEnvironment jdbcEnv) {
return Identifier.toIdentifier(tableName);
}
}
Add below property to application.properties:
spring.jpa.properties.hibernate.physical_naming_strategy=<package.name>.CustomPhysicalNamingStrategy
table.name=product
My spring-boot yaml properties look like this:
service:
mycomponent:
foo:
url: http://foo
bar:
url: http://bar
This results in the following properties being set in the Spring environment:
service.mycomponent.foo.url: http://foo
service.mycomponent.bar.url: http://bar
I'd like to define a 'mycomponent' bean if there are any properties that match service.mycomponent.[a-z]*.url. Is this possible using #ConditionalOnExpression or some other type of #Conditional?
I realize I can work around this by either adding a property such as service.mycomponent.enabled: true that could be used with #ConditionalOnProperty but I'd rather avoid that if possible.
Here's the solution I ended up taking:
Create a custom Condition which searches for any properties with a certain prefix. The RelaxedPropertyResolver has the convenient getSubProperties() method. Alternative options I found were cumbersome to iterate through the PropertySource instances.
public class MyComponentCondition extends SpringBootCondition {
#Override
public ConditionOutcome getMatchOutcome(final ConditionContext context,
final AnnotatedTypeMetadata metadata) {
final RelaxedPropertyResolver resolver = new RelaxedPropertyResolver(context.getEnvironment());
final Map<String, Object> properties = resolver.getSubProperties("service.mycomponent.");
return new ConditionOutcome(!properties.isEmpty(), "My Component");
}
}
Use that condition when setting up the bean:
#Conditional(MyComponentCondition.class)
#Bean
public MyComponent myComponent() {
return new MyComponent();
}
I'm still curious if the same thing could be done with #ConditionalOnExpression directly.
I would like to build a Spring application, where new components can be added easily and without much configuration. For example: You have different kinds of documents. These documents should be able to get exported into different fileformats.
To make this functionality easy to maintain, it should (basically) work the following way:
Someone programs the file format exporter
He/ She writes a component, which checks if the file format exporter is licensed (based on Spring Conditions). If the exporter is licensed a specialized Bean is injected in the application context.
The "whole rest" works dynamically based on the injected beans. Nothing needs to be touched in order to display it on the GUI, etc.
I pictured it the following way:
#Component
public class ExcelExporter implements Condition {
#PostConstruct
public void init() {
excelExporter();
}
#Bean
public Exporter excelExporter(){
Exporter exporter= new ExcelExporter();
return exporter;
}
#Override
public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
return true;
}
}
In order to work with those exporters (display them, etc.) I need to get all of them. I tried this:
Map<String, Exporter> exporter =BeanFactoryUtils.beansOfTypeIncludingAncestors(appContext, Exporter.class, true, true);
Unfortunate this does not work (0 beans returned). I am fairly new to this, would anyone mind to tell me how this is properly done in Spring? Maybe there is a better solution for my problem than my approach?
You can get all instances of a given type of bean in a Map effortlessly, since it's a built in Spring feature.
Simply autowire your map, and all those beans will be injected, using as a key the ID of the bean.
#Autowired
Map<String,Exporter> exportersMap;
If you need something more sophisticated, such as a specific Map implementation or a custom key. Consider defining your custom ExporterMap, as follows
#Component
class ExporterMap implements Map{
#Autowired
private Set<Exporter> availableExporters;
//your stuff here, including init if required with #PostConstruct
}