springboot屬性注入的四種方法

springBoot屬性注入的四種方法：

以注入jdbc數據源爲例

1.首先在resources下面創建application.properties文件，並添加jdbc數據源屬性

jdbc.driverClassName=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://127.0.0.1:3306/test
jdbc.username=root
jdbc.password=test

2.配置需要讀取數據源的properties類

創建類JdbcProperties

import org.springframework.boot.context.properties.ConfigurationProperties;

@ConfigurationProperties("jdbc")
public class JdbcProperties {
    private String driverClassName;
    private String url;
    private String username;
    private String password;

    public String getDriverClassName() {
        return driverClassName;
    }

    public void setDriverClassName(String driverClassName) {
        this.driverClassName = driverClassName;
    }

    public String getUrl() {
        return url;
    }

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

    public String getUsername() {
        return username;
    }

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

    public String getPassword() {
        return password;
    }

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

這裏需要引入@ConfigurationProperties("jdbc")，也就是你在applican中設置的前綴，也可以寫成@ConfigurationProperties(prefix="jdbc")

在引入的文件中其實就是按照set方式注入的屬性，同時取值的時候，通過get方法取值，所以get和set方法不能忘記添加。

3.然後就是四種注入屬性的方式了：

3.1第一種方式就是按照自動注入的方式，也就是@Autowired

import com.alibaba.druid.pool.DruidDataSource;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;

import javax.sql.DataSource;


@Configuration
@EnableConfigurationProperties(JdbcProperties.class)
public class JbdcConfiguration {

   @Autowired
   private JdbcProperties jdbcProperties;

    

    @Bean
    public DataSource dataSource(){
        DruidDataSource dataSource = new DruidDataSource();
        dataSource.setDriverClassName(this.jdbcProperties.getDriverClassName());
        dataSource.setUrl(this.jdbcProperties.getUrl());
        dataSource.setUsername(this.jdbcProperties.getUsername());
        dataSource.setPassword(this.jdbcProperties.getPassword());
        return dataSource;
    }
}

注意需要引入@EnableConfigurationProperties(JdbcProperties.class)，這個JdbcProperties是在上面創建的那個類

這樣就實現了第一種屬性注入的方式。

3.2第二種屬性注入的方式爲構造方法注入的方式

package com.w.config;
import com.alibaba.druid.pool.DruidDataSource;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;

import javax.sql.DataSource;


@Configuration
@EnableConfigurationProperties(JdbcProperties.class)
public class JConfiguration {


   private JdbcProperties jdbcProperties;

    public JConfiguration(JdbcProperties jdbcProperties) {
        this.jdbcProperties = jdbcProperties;
    }

    @Bean
    public DataSource dataSource(){
        DruidDataSource dataSource = new DruidDataSource();
        dataSource.setDriverClassName(this.jdbcProperties.getDriverClassName());
        dataSource.setUrl(this.jdbcProperties.getUrl());
        dataSource.setUsername(this.jdbcProperties.getUsername());
        dataSource.setPassword(this.jdbcProperties.getPassword());
        return dataSource;
    }
}

3.3第三種就是通過形參引入的方法注入屬性

import com.alibaba.druid.pool.DruidDataSource;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;

import javax.sql.DataSource;

@Configuration
@EnableConfigurationProperties(JdbcProperties.class)
public class JdbcConfiguration {
    
    @Bean
    public DataSource dataSource(JdbcProperties jdbcProperties){
        DruidDataSource dataSource = new DruidDataSource();
        dataSource.setDriverClassName(jdbcProperties.getDriverClassName());
        dataSource.setUrl(jdbcProperties.getUrl());
        dataSource.setUsername(jdbcProperties.getUsername());
        dataSource.setPassword(jdbcProperties.getPassword());
        return dataSource;
    }
}

3.4第四種方式就是通過引入標籤的方式，這是最簡單的方式，但是前提是對應的類中需要有set方法將值可以注入進去纔可以。

import com.alibaba.druid.pool.DruidDataSource;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;

import javax.sql.DataSource;

@Configuration
@EnableConfigurationProperties(JdbcProperties.class)
public class JdbcConfiguration {

    @Bean
    @ConfigurationProperties("jdbc")
    public DataSource dataSource(){
        DruidDataSource dataSource = new DruidDataSource();
        return dataSource;
    }
}