Java SpringBoot高级用法详解

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
<!--  该配置表示Maven坐标  -->
<!--  项目的组id  -->
    <groupId>com.jt</groupId>
<!--  项目名称  -->
    <artifactId>springboot_demo1</artifactId>
<!--  项目版本号 -->
    <version>0.0.1-SNAPSHOT</version>
    <name>springboot_demo1</name>
    <description>Demo project for Spring Boot</description>
 
    <properties>
        <java.version>1.8</java.version>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <spring-boot.version>2.4.1</spring-boot.version>
    </properties>
 
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <!--  SpringBoot的启动项   wep  相当于引入MVC框架
                    思想："开箱即用"！！！
                    说明: 只需要引入jar包,简单的配置即可以使用该功能
                 -->
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
 
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
 
    <dependencyManagement>
        <dependencies>
            <!--相当于继承了一个父级-->
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>${spring-boot.version}</version>
                <!--通过pom标识 是一个父级 -->
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>
 
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.8.1</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                    <encoding>UTF-8</encoding>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <version>2.4.1</version>
                <configuration>
                    <mainClass>com.jt.SpringbootDemo1Application</mainClass>
                </configuration>
                <executions>
                    <execution>
                        <id>repackage</id>
                        <goals>
                            <goal>repackage</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
 
</project>

#YML文件的语法
#1，数据结构  key-value结构
#2，写法：    key:(空格)value
#3，层及代码结构，注意缩进
#4，字符集 文件读取时，默认采取UTF-8编码 可以写中文
# 规则： 命名时最好指定前缀.
server:
  port: 8080
  # 指定业务的key
mysql:
  Username: root|
  Password: root||

package com.jt;
 
//import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
//import org.springframework.web.bind.annotation.RequestMapping;
 
@SpringBootApplication
public class SpringbootDemo1Application {
 
    public static void main(String[] args) {
        SpringApplication.run(SpringbootDemo1Application.class, args);
    }
 
    }

package com.jt.contraller;
 
import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
 

@RestController
public class JDBCController {
    //${key} Spring提供的springel表达式 简称为:spel表达式
    //语法: 从spring容器内部获取key,动态为属性赋值.
    @Value("${mysql.username}")
    String username;    // = "root|";
    @Value("${mysql.password}")
    String password;    // = "root";
 
    @RequestMapping("/getMsg")
    public String getMsg() {
        return "你好数据库:" + username + password;
    }
}

#默认ISO-8859-1 中文必定乱码
mysql.username2=mysql数据库
mysql.password2=你猜猜

package com.jt.contraller;
 
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.PropertySource;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@PropertySource(value="classpath:/mysql.properties",encoding = "UTF-8")
public class JDBCContraller {
    
    @Value("${mysql.username2}")
    private String username2;
    @Value("${mysql.password2")
    private String password2;
 
    @RequestMapping("/getMsg2")
    public String getMsg2(){
 
        return "你好数据库:"+ username2 +password2;
    }
}