Spring引入外部属性配置文件

我们都知道编写数据源的时候是需要连接数据库的信息的，例如：driver url username password等信息。这些信息可以单独写到一个属性配置文件中吗，这样用户修改起来会更加的方便。当然可以。

第一步：写一个数据源类，提供相关属性。

MyDataSource.java
package com.powercode.spring6.beans;

import javax.sql.DataSource;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.ConnectionBuilder;
import java.sql.SQLException;
import java.sql.SQLFeatureNotSupportedException;
import java.util.logging.Logger;

public class MyDataSource implements DataSource {
    @Override
    public String toString() {
        return "MyDataSource{" +
                "driver='" + driver + '\'' +
                ", url='" + url + '\'' +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                '}';
    }

    private String driver;
    private String url;
    private String username;
    private String password;

    public void setDriver(String driver) {
        this.driver = driver;
    }

    public void setUrl(String url) {
        this.url = url;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    @Override
    public Connection getConnection() throws SQLException {
        return null;
    }

    @Override
    public Connection getConnection(String s, String s1) throws SQLException {
        return null;
    }

    @Override
    public PrintWriter getLogWriter() throws SQLException {
        return null;
    }

    @Override
    public void setLogWriter(PrintWriter printWriter) throws SQLException {

    }

    @Override
    public void setLoginTimeout(int i) throws SQLException {

    }

    @Override
    public int getLoginTimeout() throws SQLException {
        return 0;
    }

    @Override
    public Logger getParentLogger() throws SQLFeatureNotSupportedException {
        return null;
    }

    @Override
    public ConnectionBuilder createConnectionBuilder() throws SQLException {
        return DataSource.super.createConnectionBuilder();
    }

    @Override
    public <T> T unwrap(Class<T> aClass) throws SQLException {
        return null;
    }

    @Override
    public boolean isWrapperFor(Class<?> aClass) throws SQLException {
        return false;
    }
}

jdbc.properties

driver=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/spring
username=root
password=root123

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd">
    <context:property-placeholder location="jdbc.properties"/>
    <bean id="dataSource" class="com.powercode.spring6.beans.MyDataSource">
        <property name="driver" value="${driver}"></property>
        <property name="url" value="${url}"></property>
        <property name="username" value="${username}"></property>
        <property name="password" value="${password}"></property>
    </bean>
</beans>

   xmlns:context="http://www.springframework.org/schema/context"

在beans里面添加了这个字段，还有 <context:property-placeholder location="jdbc.properties"/>
后面就可以使用其中的key对应的value值了

测试函数

    @Test
    public void testPropertiesSpringCode(){
        Logger logger = LoggerFactory.getLogger(FirstSpringTest.class);
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("spring_jdbc.xml");
        MyDataSource myDataSource = applicationContext.getBean("dataSource",MyDataSource.class);
        logger.info(myDataSource.toString());
    }

/usr/lib/jvm/java-17-openjdk/bin/java -ea -Didea.test.cyclic.buffer.size=1048576 -javaagent:/opt/intellij-idea-ultimate-edition/lib/idea_rt.jar=35121:/opt/intellij-idea-ultimate-edition/bin -Dfile.encoding=UTF-8 -classpath /home/meowrain/.m2/repository/org/junit/platform/junit-platform-launcher/1.10.1/junit-platform-launcher-1.10.1.jar:/home/meowrain/.m2/repository/org/junit/platform/junit-platform-engine/1.10.1/junit-platform-engine-1.10.1.jar:/home/meowrain/.m2/repository/org/junit/jupiter/junit-jupiter-engine/5.10.1/junit-jupiter-engine-5.10.1.jar:/opt/intellij-idea-ultimate-edition/lib/idea_rt.jar:/opt/intellij-idea-ultimate-edition/plugins/junit/lib/junit5-rt.jar:/opt/intellij-idea-ultimate-edition/plugins/junit/lib/junit-rt.jar:/home/meowrain/IdeaProjects/spring_first/target/test-classes:/home/meowrain/IdeaProjects/spring_first/target/classes:/home/meowrain/.m2/repository/org/springframework/spring-context/6.1.0-SNAPSHOT/spring-context-6.1.0-20231116.112758-846.jar:/home/meowrain/.m2/repository/org/springframework/spring-aop/6.1.0-SNAPSHOT/spring-aop-6.1.0-20231116.112758-846.jar:/home/meowrain/.m2/repository/org/springframework/spring-beans/6.1.0-SNAPSHOT/spring-beans-6.1.0-20231116.112758-846.jar:/home/meowrain/.m2/repository/org/springframework/spring-core/6.1.0-SNAPSHOT/spring-core-6.1.0-20231116.112758-846.jar:/home/meowrain/.m2/repository/org/springframework/spring-jcl/6.1.0-SNAPSHOT/spring-jcl-6.1.0-20231116.112758-846.jar:/home/meowrain/.m2/repository/org/springframework/spring-expression/6.1.0-SNAPSHOT/spring-expression-6.1.0-20231116.112758-846.jar:/home/meowrain/.m2/repository/io/micrometer/micrometer-observation/1.12.0/micrometer-observation-1.12.0.jar:/home/meowrain/.m2/repository/io/micrometer/micrometer-commons/1.12.0/micrometer-commons-1.12.0.jar:/home/meowrain/.m2/repository/org/junit/jupiter/junit-jupiter-api/5.10.1/junit-jupiter-api-5.10.1.jar:/home/meowrain/.m2/repository/org/opentest4j/opentest4j/1.3.0/opentest4j-1.3.0.jar:/home/meowrain/.m2/repository/org/junit/platform/junit-platform-commons/1.10.1/junit-platform-commons-1.10.1.jar:/home/meowrain/.m2/repository/org/apiguardian/apiguardian-api/1.1.2/apiguardian-api-1.1.2.jar:/home/meowrain/.m2/repository/org/apache/logging/log4j/log4j-core/2.19.0/log4j-core-2.19.0.jar:/home/meowrain/.m2/repository/org/apache/logging/log4j/log4j-api/2.19.0/log4j-api-2.19.0.jar:/home/meowrain/.m2/repository/org/apache/logging/log4j/log4j-slf4j2-impl/2.19.0/log4j-slf4j2-impl-2.19.0.jar:/home/meowrain/.m2/repository/org/slf4j/slf4j-api/2.0.0/slf4j-api-2.0.0.jar com.intellij.rt.junit.JUnitStarter -ideVersion5 -junit5 com.powercode.spring6.test.FirstSpringTest,testPropertiesSpringCode
2024-01-10 09:45:32 341 [main] DEBUG org.springframework.context.support.ClassPathXmlApplicationContext - Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@62ea3440
2024-01-10 09:45:32 447 [main] DEBUG org.springframework.beans.factory.xml.XmlBeanDefinitionReader - Loaded 2 bean definitions from class path resource [spring_jdbc.xml]
2024-01-10 09:45:32 459 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'org.springframework.context.support.PropertySourcesPlaceholderConfigurer#0'
2024-01-10 09:45:32 484 [main] DEBUG org.springframework.core.env.PropertySourcesPropertyResolver - Found key 'driver' in PropertySource 'localProperties' with value of type String
2024-01-10 09:45:32 484 [main] DEBUG org.springframework.core.env.PropertySourcesPropertyResolver - Found key 'url' in PropertySource 'localProperties' with value of type String
2024-01-10 09:45:32 484 [main] DEBUG org.springframework.core.env.PropertySourcesPropertyResolver - Found key 'username' in PropertySource 'localProperties' with value of type String
2024-01-10 09:45:32 485 [main] DEBUG org.springframework.core.env.PropertySourcesPropertyResolver - Found key 'password' in PropertySource 'localProperties' with value of type String
2024-01-10 09:45:32 487 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'dataSource'
2024-01-10 09:45:32 497 [main] INFO com.powercode.spring6.test.FirstSpringTest - MyDataSource{driver='com.mysql.cj.jdbc.Driver', url='jdbc:mysql://localhost:3306/spring', username='root', password='root123'}

进程已结束，退出代码为 0