1、實現方式一：Spring中的@PropertySource

@Component
@PropertySource("classpath:user.properties")
public class UserInfo {
 @Value("${user.username}")
 private String username;

 @Value("${user.password}")
 private String password;

 @Value("${user.age}")
 private Integer age;

 @Override
 public String toString() {
 return "UserInfo{" +
  "username='" + username + '\'' +
  ",password='" + password + '\'' +
  ",age=" + age +
  '}';
 }
}

配置檔案中：

user.username='admin'
user.password='123'
user.age=88

測試：

@SpringBootTest
public class UserInfoTest {
 @Autowired
 UserInfo userInfo;
 @Test
 public void user(){
 System.out.println(userInfo.toString());
 }
}

結果：

UserInfo{username=''admin'',password=''123'',age=88}

注意：此方法是不安全的，如果在配置檔案中找不到對應的屬性，例如沒有username屬性，會報錯如下：

java.lang.IllegalStateException: Failed to load ApplicationContext
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'userInfo': Injection of autowired dependencies failed; nested exception is java.lang.IllegalArgumentException: Could not resolve placeholder 'user.username' in value "${user.username}"

2、實現方式二：通過SpringBoot特有的@ConfigurationProperties來實現

注意點： 需要getter、setter函式

@Component
@PropertySource("classpath:user.properties")
@ConfigurationProperties(prefix = "user")
public class UserInfo {
// @Value("${user.username}")
 private String username;

// @Value("${user.password}")
 private String password;

// @Value("${user.age}")
 private Integer age;


 public String getUsername() {
 return username;
 }

 public String getPassword() {
 return password;
 }

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

 public Integer getAge() {
 return age;
 }

 public void setAge(Integer age) {
 this.age = age;
 }

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

 @Override
 public String toString() {
 return "UserInfo{" +
  "username='" + username + '\'' +
  ",age=" + age +
  '}';
 }
}

這種方法比較安全，即使配置檔案中沒有對於屬性，也不會丟擲異常。

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