Context:property-placeholder

This is very common in the spring configuration file.

Context:property-placeholder greatly facilitates the configuration of our database.

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2. Just add a line to the spring configuration file:<context:property-placeholder? location="classpath:jdbc.properties"/> The location value is the position of the parameter profile, and the parameter profile is usually placed in the SRC directory. The format of the parameter configuration file is the same as the Java common parameter configuration file, which is the form of key-value pairs, for example:
6. #jdbc配置
10. Test.jdbc.driverclassname=Com.mysql.jdbc.Driver
12. Test.jdbc.url=jdbc:mysql://localhost:3306/test
14. Test.jdbc.username=Root
16. test.jdbc.password=Root

This allows you to set values for the properties of the bean that is configured for spring, such as spring has a JDBC data source class Drivermanagerdatasource

This defines the bean in the configuration file:

<bean id= "Testdatasource" class= "Org.springframework.jdbc.datasource.DriverManagerDataSource" >
<property name= "Driverclassname" value= "${test.jdbc.driverclassname}"/>
<property name= "url" value= "${test.jdbc.url}"/>
<property name= "username" value= "${test.jdbc.username}"/>
<property name= "Password" value= "${test.jdbc.password}"/>
</bean>

This modification is also convenient, but also unified this specification.

It is also important to note that if you encounter the following problem:

Both A and B modules have their own spring XML configuration, each with its own configuration file:

The spring configuration file for the A module is as follows:

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2. <? XML version= "1.0" encoding="UTF-8" ?>
4. <beans xmlns="Http://www.springframework.org/schema/beans"
6. xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
8. xmlns:context="Http://www.springframework.org/schema/context"
10. xmlns:p="http://www.springframework.org/schema/p"
12. xsi:schemalocation= "Http://www.springframework.org/schema/beans Http://www.springframework.org/schema/beans /spring-beans-3.2.xsd
14. Http://www.springframework.org/schema/context http://www.springframework.org/schema/context/ Spring-context-3.2.xsd ">
16. <context:property-placeholder location="classpath*:conf/conf_a.properties"/>
18. <Bean class="Com.xxx.aaa.Bean1"
20. p:driverclassname="${modulea.jdbc.driverclassname}"
22. p:url="${modulea.jdbc.url}"
24. p:username="${modulea.jdbc.username}"
26. p:password="${modulea.jdbc.password}"/>
28. </Beans>

Conf/conf_a.properties:
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1. Modulea.jdbc.driverclassname=Com.mysql.jdbc.Driver
2. Modulea.jdbc.username=Cartan
3. modulea.jdbc.password=Superman
4. Modulea.jdbc.url=Jdbc:mysql://127.0.0.1:3306/modulea? useunicode=true&characterencoding=UTF8

The spring configuration file for the B module is as follows:
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2. <? XML version= "1.0" encoding="UTF-8" ?>
4. <beans xmlns="Http://www.springframework.org/schema/beans"
6. xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
8. xmlns:context="Http://www.springframework.org/schema/context"
10. xmlns:p="http://www.springframework.org/schema/p"
12. xsi:schemalocation= "Http://www.springframework.org/schema/beans Http://www.springframework.org/schema/beans /spring-beans-3.2.xsd
14. Http://www.springframework.org/schema/context http://www.springframework.org/schema/context/ Spring-context-3.2.xsd ">
16. <context:property-placeholder location="classpath*:conf/conf_b.properties"/>
18. <Bean class="Com.xxx.bbb.Bean1"
20. p:driverclassname="${moduleb.jdbc.driverclassname}"
22. p:url="${moduleb.jdbc.url}"
24. p:username="${moduleb.jdbc.username}"
26. p:password="${moduleb.jdbc.password}"/>
28. </Beans>

Conf/conf_b.properties:
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1. Moduleb.jdbc.driverclassname=Com.mysql.jdbc.Driver
2. Moduleb.jdbc.username=Cartan
3. moduleb.jdbc.password=Superman
4. Moduleb.jdbc.url=Jdbc:mysql://127.0.0.1:3306/modulea? useunicode=true&characterencoding=UTF8

It is normal to run a module alone or run the B module separately, but after integrating A and B two modules, the spring container will not start:
Could not resolve placeholder ' moduleb.jdbc.driverClassName ' in string value "${moduleb.jdbc.driverclassname}"
Cause: The spring container uses the discovery mechanism of reflection scanning, A bean that detects a org.springframework.beans.factory.config.PropertyPlaceholderConfigurer in the spring container stops the remaining propertyplaceholderconf Scanning of Igurer

Only one context:property-placeholder can be defined in the spring container, or there will be such a mistake, how to solve the above problem?

A and B modules removed

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1. <context:property-placeholder location="classpath*:conf/conf_b.properties"/>

Then write an XML again:

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2. <? XML version= "1.0" encoding="UTF-8" ?>
4. <beans xmlns="Http://www.springframework.org/schema/beans"
6. xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
8. xmlns:context="Http://www.springframework.org/schema/context"
10. xmlns:p="http://www.springframework.org/schema/p"
12. xsi:schemalocation= "Http://www.springframework.org/schema/beans Http://www.springframework.org/schema/beans /spring-beans-3.2.xsd
14. Http://www.springframework.org/schema/context http://www.springframework.org/schema/context/ Spring-context-3.2.xsd ">
16. <context:property-placeholder location="classpath*:conf/conf*.properties"/>
18. <import resource="A.xml"/>
20. <import resource="B.xml"/>
22. </Beans>

Context:property-placeholder