SpringBoot中Condition下常用条件依赖注解详细介绍及案例使用
@ConditionalOnClass() Spring中存在指定class对象时，注入指定配置@ConditionalOnMissingClass() Spring中不存在指定class对象时，注入指定配置@ConditionalOnBean() 根据ioc中判断有没有此实例对象,有则加载指定配置ConditionalOnMissingBean() 根据ioc中判断有没有此实例对象,没有则加载指定配置@ConditionalOnProperty() 配置文件中配置的指定参数值符合要求时，加载此配置@ConditionalOnExpression() 配置文件中配置的指定参数值与我给的值比较为true时，加载此配置@ConditionalOnResource() 指定的资源文件出现在classpath中生效(就是编译后target里classes里的路径名是否存在)链接：[condition包下常用注解案例源代码下载地址](https://download.csdn.net/download/JAVA_MHH/16311322)
@ConditionalOnClass() Spring中存在指定class对象时，注入指定配置
和ConditionalOnBean()的区别在于ConditionalOnBean()是根据ioc里是否有此实例对象，而ConditionalOnClass()表示只要在Spring中有这个类就可以
1.首先引入pom依赖
2.实体类测试对象
根据Condition返回结果表示是否将此对象注入ioc中; true:表示注入ioc
//根据Condition返回结果表示是否注入ioc中true：表示注入ioc
public class Student {
String name="小白";
Integer age =12;
@Override
public String toString() {
return "Student{" +
"name='" + name + '\'' +
", age=" + age +
'}';
}
}
3.定义@ConditionalOnClass（）配置类
name = “com.alibaba.fastjson.JSON” 表示此spring中是否有这个类，有的话就注入此配置到ioc
import com.it.mhh.entry.Student;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class CustomConditionOnClass {
@Bean
@ConditionalOnClass(name = "com.alibaba.fastjson.JSON")
//这里就是判断是否吧此对象注入IOC，ClassCondition此类matches对象的返回的Boolean[true：创建，false：不创建]
public Student getStudent() {
return new Student();
}
}
4.启动类测试
@ConditionalOnClass() Spring中存在指定class，对应该配置才会生效
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
//@ConditionalOnClass() Spring中存在指定class，对应该配置才会生效
@SpringBootApplication
public class ConditionApplication {
public static void main(String[] args) {
ConfigurableApplicationContext run = SpringApplication.run(ConditionApplication.class, args);
//Exception in thread "main" org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'getStudent' available[表示没有获取到这个bean]
Object getStudent = run.getBean("getStudent");//这里因为是注入ioc时 @Bean没有指定名字，则就是方法名从ioc中获取此对象
System.out.println(getStudent); //Student{name='小白', age=12}
}
}
-------------------------------------------------------------------------------------------------------------------------------------------------------------
@ConditionalOnMissingClass() Spring中不存在指定class对象时，注入指定配置
和ConditionalOnMissingBean()的区别在于ConditionalOnMissingBean()是根据ioc里没有此实例对象，而ConditionalOnClass()表示只要在Spring中没有这个类就可以
1.首先引入pom依赖
2.实体类测试对象
根据Condition返回结果表示是否将此对象注入ioc中; true:表示注入ioc
//根据Condition返回结果表示是否注入ioc中true：表示注入ioc
public class Student {
String name="小白";
Integer age =12;
@Override
public String toString() {
return "Student{" +
"name='" + name + '\'' +
", age=" + age +
'}';
}
}
3.定义@ConditionalOnMissingClass（）配置类
name = “com.alibaba.fastjson.JSON” 表示此spring中是否有这个类，有的话就不注入此配置到ioc
import com.it.mhh.entry.Student;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingClass;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class CustomConditionOnMissingClass {
@Bean
@ConditionalOnMissingClass("com.alibaba.fastjson.JSON")
//这里就是判断是否吧此对象注入IOC，ClassCondition此类matches对象的返回的Boolean[true：创建，false：不创建]
public Student getStudent() {
return new Student();
}
}
4.启动类测试
@ConditionalOnMissingClass Spring容器中不存在指定class，注入指定配置
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
//@ConditionalOnMissingClass Spring容器中不存在指定class，注入指定配置
@SpringBootApplication
public class ConditionApplication {
public static void main(String[] args) {
ConfigurableApplicationContext run = SpringApplication.run(ConditionApplication.class, args);
//Exception in thread "main" org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'getStudent' available[表示没有获取到这个bean]
Object getStudent = run.getBean("getStudent");//这里因为是注入ioc时 @Bean没有指定名字，则就是方法名从ioc中获取此对象
System.out.println(getStudent); //Student{name='小白', age=12}
}
}
-------------------------------------------------------------------------------------------------------------------------------------------------------------
@ConditionalOnBean() 根据ioc中判断有没有此实例对象,有则加载指定配置
和ConditionalOnClass()的区别在于ConditionalOnClass()是根据Spring中是否有此类，而ConditionalOnBean()表示在ioc中是否由此实例对象；
1.首先引入pom依赖
2.实体类测试对象
根据Condition返回结果表示是否将此对象注入ioc中; true:表示注入ioc
//根据Condition返回结果表示是否注入ioc中true：表示注入ioc
public class Student {
String name="小白";
Integer age =12;
@Override
public String toString() {
return "Student{" +
"name='" + name + '\'' +
", age=" + age +
'}';
}
}
2.1 引入条件判断实体类
将此类注入ioc容器
importorg.springframework.stereotype.Component;
@Component
Public class BeanServer{
}
3.定义@ConditionalOnBean（）配置类
BeanServer.class :判断ioc中是否有此类对象，有的话就加载此配置
import com.it.mhh.customConditionOnBeanOrOnMissingBean.server.TestServer;
import com.it.mhh.entry.Student;
import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class CustomConditionOnBean {
@Bean
@ConditionalOnBean(BeanServer.class)
//这里就是判断是否吧此对象注入IOC，ClassCondition此类matches对象的返回的Boolean[true：创建，false：不创建]
public Student getStudent() {
return new Student();
}
}
4.启动类测试
@ConditionalOnBean() Spring容器中存在指定class实例对象时，注入指定配置
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
//@ConditionalOnBean() Spring容器中存在指定class实例对象时，注入指定配置
@SpringBootApplication
public class ConditionApplication {
public static void main(String[] args) {
ConfigurableApplicationContext run = SpringApplication.run(ConditionApplication.class, args);
//Exception in thread "main" org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'getStudent' available[表示没有获取到这个bean]
Object getStudent = run.getBean("getStudent");//这里因为是注入ioc时 @Bean没有指定名字，则就是方法名从ioc中获取此对象
System.out.println(getStudent); //Student{name='小白', age=12}
}
}
-------------------------------------------------------------------------------------------------------------------------------------------------------------
ConditionalOnMissingBean() 根据ioc中判断有没有此实例对象,没有则加载指定配置
和ConditionalOnMissingClass()的区别在于ConditionalOnMissingClass()是根据Spring中是否有此类，而ConditionalOMissingnBean()表示在ioc中是否由此实例对象；
1.首先引入pom依赖
2.实体类测试对象
根据Condition返回结果表示是否将此对象注入ioc中; true:表示注入ioc
//根据Condition返回结果表示是否注入ioc中true：表示注入ioc
public class Student {
String name="小白";
Integer age =12;
@Override
public String toString() {
return "Student{" +
"name='" + name + '\'' +
", age=" + age +
'}';
}
}
2.1 引入条件判断实体类
不注入此类到ioc容器
importorg.springframework.stereotype.Component;
//@Component
Public class BeanServer{
}
3定义@ConditionalOnMissingBean（）配置类
BeanServer.class :判断ioc中是否有此类对象，没有的话就加载此配置
import com.it.mhh.customConditionOnBeanOrOnMissingBean.server.TestServer;
import com.it.mhh.entry.Student;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
//@Configuration
public class CustomConditionOnMissingBean {
@Bean
@ConditionalOnMissingBean(BeanServer.class)
//这里就是判断是否吧此对象注入IOC，ClassCondition此类matches对象的返回的Boolean[true：创建，false：不创建]
public Student getStudent() {
return new Student();
}
}
4.启动类测试
@ConditionalOnMissingBean() Spring ioc中不存在指定class实例对象时，注入指定配置
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
//@ConditionalOnMissingBean() Spring容器中不存在指定class实例对象时，注入指定配置
@SpringBootApplication
public class ConditionApplication {
public static void main(String[] args) {
ConfigurableApplicationContext run = SpringApplication.run(ConditionApplication.class, args);
//Exception in thread "main" org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'getStudent' available[表示没有获取到这个bean]
Object getStudent = run.getBean("getStudent");//这里因为是注入ioc时 @Bean没有指定名字，则就是方法名从ioc中获取此对象
System.out.println(getStudent); //Student{name='小白', age=12}
}
}
-------------------------------------------------------------------------------------------------------------------------------------------------------------
@ConditionalOnProperty() 配置文件中配置的指定参数值符合要求时，加载此配置
与@ConditionalOnExpression()的区别在于@ConditionalOnProperty() 注解使用的是通过注解中的属性赋值作为参照物和yml里的配置进行匹配是否为相同；
1.首先引入pom依赖
2.实体类测试对象
根据Condition返回结果表示是否将此对象注入ioc中; true:表示注入ioc
//根据Condition返回结果表示是否注入ioc中true：表示注入ioc
public class Student {
String name="小白";
Integer age =12;
@Override
public String toString() {
return "Student{" +
"name='" + name + '\'' +
", age=" + age +
'}';
}
}
3定义@ConditionalOnProperty() 配置类
prefix = “class”,name = “teacher”,matchIfMissing=false, havingValue = “小黑” @ConditionalOnProperty()中属性含义 public @interface ConditionalOnProperty { String[] value() default {}; // 数组，获取对应yml名称的key，与name含义一样，不能同时使用value和name; String prefix() default ""; //配置文件中yml名称的前缀; String[] name() default {};// 数组，获取对应yml名称的key，与value含义一样，不能同时使用value和name; String havingValue() default ""; //配置文件yml的value值 boolean matchIfMissing() default false; //配置文件yml中没有与之匹配到的数值，是否加载，true：表示正常加载此配置，false表示如果yml中没有此数值就不加载； }
import com.it.mhh.entry.Student;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class CustomConditionOnProperty {
@Bean
@ConditionalOnProperty(prefix = "class",name = "teacher",matchIfMissing=false, havingValue = "小黑")
//这里就是判断是否吧此对象注入IOC，ClassCondition此类matches对象的返回的Boolean[true：创建，false：不创建]
public Student getStudent() {
return new Student();
}
}
4 application.yml配置
@ConditionalOnProperty()注解中的 prefix 属性就是此yml配的前缀 yml，name就是 teacher，而havingValue 则就是’小黑’，如果application中有此配置，则加载相应配置
class:
teacher: 小黑
5.启动类测试
@ConditionalOnProperty()配置文件中配置的指定参数值符合要求时，加载此配置
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
// @ConditionalOnProperty()配置文件中配置的指定参数值符合要求时，加载此配置
@SpringBootApplication
public class ConditionApplication {
public static void main(String[] args) {
ConfigurableApplicationContext run = SpringApplication.run(ConditionApplication.class, args);
//Exception in thread "main" org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'getStudent' available[表示没有获取到这个bean]
Object getStudent = run.getBean("getStudent");//这里因为是注入ioc时 @Bean没有指定名字，则就是方法名从ioc中获取此对象
System.out.println(getStudent); //Student{name='小白', age=12}
}
}
-------------------------------------------------------------------------------------------------------------------------------------------------------------
@ConditionalOnExpression() 配置文件中配置的指定参数值与我给的值比较为true时，加载此配置
与@ConditionalOnProperty() 的区别在于@ConditionalOnExpression()注解使用的是SpringEL表达式与我给的值进行匹配，为true时加载配置,而@ConditionalOnProperty() 注解使用的是通过注解中的属性赋值作为参照物和yml里的配置进行匹配是否为相同；
1.首先引入pom依赖
2.实体类测试对象
根据Condition返回结果表示是否将此对象注入ioc中; true:表示注入ioc
//根据Condition返回结果表示是否注入ioc中true：表示注入ioc
public class Student {
String name="小白";
Integer age =12;
@Override
public String toString() {
return "Student{" +
"name='" + name + '\'' +
", age=" + age +
'}';
}
}
3.定义@ConditionalOnExpression() 配置类
“’${class.teacher}’.equals(‘小黑’)” :Spring EL表达式 ，配置文件class.teacher里对应的值去比较我输入的’小黑‘是否相同，true:加载此配置；
import com.it.mhh.entry.Student;
import org.springframework.boot.autoconfigure.condition.ConditionalOnExpression;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class CustomConditionOnExpression {
@Bean
//配置文件中配置的指定参数值与我要做比较的值为true时，加载此配置
@ConditionalOnExpression("'${class.teacher}'.equals('小黑')")
//这里就是判断是否吧此对象注入IOC，ClassCondition此类matches对象的返回的Boolean[true：创建，false：不创建]
public Student getStudent() {
return new Student();
}
}
4 application.yml配置
@ConditionalOnExpression()注解 value属性就是此配置的键 class.teacherg 而获取到的值就是’小黑‘，然后进行比较， true则加载相应配置
class:
teacher: 小黑
5.启动类测试
@ConditionalOnExpression()//配置文件中配置的指定参数值与我传的参数进行比较，如果相同则为true，加载此配置，否则不加载
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
// @ConditionalOnExpression()//配置文件中配置的指定参数值与我传的参数比较，相同为true时，加载此配置
@SpringBootApplication
public class ConditionApplication {
public static void main(String[] args) {
ConfigurableApplicationContext run = SpringApplication.run(ConditionApplication.class, args);
//Exception in thread "main" org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'getStudent' available[表示没有获取到这个bean]
Object getStudent = run.getBean("getStudent");//这里因为是注入ioc时 @Bean没有指定名字，则就是方法名从ioc中获取此对象
System.out.println(getStudent);
}
}
-------------------------------------------------------------------------------------------------------------------------------------------------------------
@ConditionalOnResource() 指定的资源文件出现在classpath中生效(就是编译后target里classes里的路径名是否存在)
指定文件路径名存在时，对应配置生效
1.首先引入pom依赖
2.实体类测试对象
根据Condition返回结果表示是否将此对象注入ioc中; true:表示注入ioc
//根据Condition返回结果表示是否注入ioc中true：表示注入ioc
public class Student {
String name="小白";
Integer age =12;
@Override
public String toString() {
return "Student{" +
"name='" + name + '\'' +
", age=" + age +
'}';
}
}
定义@ConditionalOnResource()配置类
resources = “com\it\mhh” :编译后taget->classes里的路径名是否存在，存在为true，加载配置
import com.it.mhh.entry.Student;
import org.springframework.boot.autoconfigure.condition.ConditionalOnResource;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class CustomConditionOnResource {
@Bean
//指定的资源文件出现在classpath中生效(就数编译后target里classes里的包路径)
@ConditionalOnResource(resources = "com\\it\\mhh")
//这里就是判断是否吧此对象注入IOC，ClassCondition此类matches对象的返回的Boolean[true：创建，false：不创建]
public Student getStudent() {
return new Student();
}
}
4.启动类测试
@ConditionalOnResource()//指定的资源文件出现在classpath中生效(就数编译后target里classes里的包路径)
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
@SpringBootApplication
//@ConditionalOnResource()//指定的资源文件出现在classpath中生效(就数编译后target里classes里的包路径)
public class ConditionApplication {
public static void main(String[] args) {
ConfigurableApplicationContext run = SpringApplication.run(ConditionApplication.class, args);
//Exception in thread "main" org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'getStudent' available[表示没有获取到这个bean]
Object getStudent = run.getBean("getStudent");//这里因为是注入ioc时 @Bean没有指定名字，则就是方法名从ioc中获取此对象
System.out.println(getStudent);
}
}
链接：condition包下常用注解案例源代码下载地址