Spring @Value always gives an error if property is Integer

问题

I am using sprin version 4.3.8.RELEASE. also i am using @Value to inject values from property file, if the properties are string that no problem, but if the property is Integer that is a problem (i know there is many questions about this i tried all the answers but the issue still exist)

The property is

CONNECTION.TIME.OUT=100000

First solution

@Value("${CONNECTION.TIME.OUT}")
protected Integer connectionTimeOut;

Ecxeption

Failed to convert value of type 'java.lang.String' to required type 'java.lang.Integer'; nested exception is java.lang.NumberFormatException: For input string: "${CONNECTION.TIME.OUT}"

Second solution

@Value("#{new Integer('${CONNECTION.TIME.OUT}')}")
protected Integer connectionTimeOut;

Exception

EL1003E: A problem occurred whilst attempting to construct an object of type 'Integer' using arguments '(java.lang.String)'

Third solution

@Value("#{new Integer.parseInteger('${CONNECTION.TIME.OUT}')}")
protected Integer connectionTimeOut;

Exception

EL1003E: A problem occurred whilst attempting to construct an object of type 'Integer' using arguments '(java.lang.String)'

any ideas why is that

回答1:

For @Value("${CONNECTION.TIME.OUT}") your error is java.lang.NumberFormatException: For input string: "${CONNECTION.TIME.OUT}". This means that expression was not processed resulting in Integer.parseInt("${CONNECTION.TIME.OUT}") which thrown the NumberFormatException.

Either there is no PropertyPlaceholderConfigurer bean registered in the Spring context and @Value annotations are not processed or there is no property CONNECTION.TIME.OUT defined.

回答2:

To avoid such type of situation where the exception occurs due to un-availibilty of the property, Add default value in the tag. If property is not available then it will populate the default value

@Value("${CONNECTION.TIME.OUT:10}")

回答3:

Your property file is probably not loaded properly.

When provided with no valid value for a property placeholder, Spring will automatically try to assign this value to the name of the @Value annotation. In your case, this:

@Value("#{new Integer('${CONNECTION.TIME.OUT}')}")
protected Integer connectionTimeOut;

Is interpreted as:

protected Integer connectionTimeOut = new Integer("${CONNECTION.TIME.OUT}");

Which, indeed, brings an error.

---

Try to either configure a PropertyPlaceholderConfigurer in your beans, or make sure that your property file is loaded properly in your classpath by your configuration. Something among the lines of:

<context:property-placeholder
    ignore-unresolvable="true" 
    location="classpath:yourfile.properties" />

In your configuration file will help, in this case.

来源：https://stackoverflow.com/questions/49793547/spring-value-always-gives-an-error-if-property-is-integer