springboot 注解说明（@ConditionalOnProperty）
应用：根据配置文件的属性决定是否将类注册为bean
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相关类与注解
@ConditionalOnProperty：标注在类或者方法上
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE, ElementType.METHOD})
@Documented
@Conditional({OnPropertyCondition.class})
public @interface ConditionalOnProperty {
String[] value() default {};
String prefix() default "";
String[] name() default {};
String havingValue() default "";
boolean matchIfMissing() default false;
}
说明：value与name等效，同时配置时，优先使用value；
匹配的key：prefix+"."+name，
若含有key，且设置了havingValue，若key对应的value=havingvalue，则匹配，若value与havingValue不等，则不匹配
若含有key，且没有设置havingValue，若key对应的value不为false，则匹配，若value为false，则不匹配
如不包含key，且设置了matchingIfMissing=true，则匹配，若matchingIfMissing=false，则不匹配
@Conditional
@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Conditional {
Class<? extends Condition>[] value(); //继承condition的类数组
}
Condition
@FunctionalInterface
public interface Condition {
boolean matches(ConditionContext var1, AnnotatedTypeMetadata var2);
}
OnPropertyCondition
@Order(-2147483608)
class OnPropertyCondition extends SpringBootCondition {
OnPropertyCondition() {
}
public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) {
//获取匹配结果
List<AnnotationAttributes> allAnnotationAttributes = this.annotationAttributesFromMultiValueMap(metadata.getAllAnnotationAttributes(ConditionalOnProperty.class.getName()));
List<ConditionMessage> noMatch = new ArrayList();
List<ConditionMessage> match = new ArrayList();
Iterator var6 = allAnnotationAttributes.iterator();
while(var6.hasNext()) {
AnnotationAttributes annotationAttributes = (AnnotationAttributes)var6.next();
ConditionOutcome outcome = this.determineOutcome(annotationAttributes, context.getEnvironment());
(outcome.isMatch() ? match : noMatch).add(outcome.getConditionMessage());
}
if (!noMatch.isEmpty()) {
return ConditionOutcome.noMatch(ConditionMessage.of(noMatch));
} else {
return ConditionOutcome.match(ConditionMessage.of(match));
}
}
private List<AnnotationAttributes> annotationAttributesFromMultiValueMap(MultiValueMap<String, Object> multiValueMap) {
//将属性转换为List<AnnotationAttributes>
List<Map<String, Object>> maps = new ArrayList();
multiValueMap.forEach((key, value) -> {
for(int i = 0; i < value.size(); ++i) {
Object map;
if (i < maps.size()) {
map = (Map)maps.get(i);
} else {
map = new HashMap();
maps.add(map);
}
((Map)map).put(key, value.get(i));
}
});
List<AnnotationAttributes> annotationAttributes = new ArrayList(maps.size());
Iterator var4 = maps.iterator();
while(var4.hasNext()) {
Map<String, Object> map = (Map)var4.next();
annotationAttributes.add(AnnotationAttributes.fromMap(map));
}
return annotationAttributes;
}
private ConditionOutcome determineOutcome(AnnotationAttributes annotationAttributes, PropertyResolver resolver) {
OnPropertyCondition.Spec spec = new OnPropertyCondition.Spec(annotationAttributes);
List<String> missingProperties = new ArrayList();
List<String> nonMatchingProperties = new ArrayList();
spec.collectProperties(resolver, missingProperties, nonMatchingProperties);
if (!missingProperties.isEmpty()) {
return ConditionOutcome.noMatch(ConditionMessage.forCondition(ConditionalOnProperty.class, new Object[]{spec}).didNotFind("property", "properties").items(Style.QUOTE, missingProperties));
} else {
return !nonMatchingProperties.isEmpty() ? ConditionOutcome.noMatch(ConditionMessage.forCondition(ConditionalOnProperty.class, new Object[]{spec}).found("different value in property", "different value in properties").items(Style.QUOTE, nonMatchingProperties)) : ConditionOutcome.match(ConditionMessage.forCondition(ConditionalOnProperty.class, new Object[]{spec}).because("matched"));
}
}
private static class Spec {
private final String prefix;
private final String havingValue;
private final String[] names;
private final boolean matchIfMissing;
Spec(AnnotationAttributes annotationAttributes) {
String prefix = annotationAttributes.getString("prefix").trim();
if (StringUtils.hasText(prefix) && !prefix.endsWith(".")) {
prefix = prefix + ".";
}
this.prefix = prefix;
this.havingValue = annotationAttributes.getString("havingValue");
this.names = this.getNames(annotationAttributes);
this.matchIfMissing = annotationAttributes.getBoolean("matchIfMissing");
}
private String[] getNames(Map<String, Object> annotationAttributes) {
String[] value = (String[])((String[])annotationAttributes.get("value"));
String[] name = (String[])((String[])annotationAttributes.get("name"));
Assert.state(value.length > 0 || name.length > 0, "The name or value attribute of @ConditionalOnProperty must be specified");
Assert.state(value.length == 0 || name.length == 0, "The name and value attributes of @ConditionalOnProperty are exclusive");
return value.length > 0 ? value : name;
} //name与value如果同时配置，优先使用value
private void collectProperties(PropertyResolver resolver, List<String> missing, List<String> nonMatching) {
String[] var4 = this.names;
int var5 = var4.length;
for(int var6 = 0; var6 < var5; ++var6) {
String name = var4[var6];
String key = this.prefix + name; //key：prefix+"."+name
if (resolver.containsProperty(key)) {
if (!this.isMatch(resolver.getProperty(key), this.havingValue)) {
nonMatching.add(name);
} //如果含有key，且key对应的值不与havingValue匹配，将name添加进nonMatching中
} else if (!this.matchIfMissing) {
missing.add(name);
} //如果不包含key，则matchingIfMissing=true，不添加进missing中，为false是添加进missing中
}
}
private boolean isMatch(String value, String requiredValue) {
if (StringUtils.hasLength(requiredValue)) {
return requiredValue.equalsIgnoreCase(value); //如果设置了havingValue，value与havingValue相等则匹配，否则不匹配
} else {
return !"false".equalsIgnoreCase(value);
} //如果没有设置havingValue，value只要不为false则匹配，value为false则不匹配
}
public String toString() {
StringBuilder result = new StringBuilder();
result.append("(");
result.append(this.prefix);
if (this.names.length == 1) {
result.append(this.names[0]);
} else {
result.append("[");
result.append(StringUtils.arrayToCommaDelimitedString(this.names));
result.append("]");
}
if (StringUtils.hasLength(this.havingValue)) {
result.append("=").append(this.havingValue);
}
result.append(")");
return result.toString();
}
}
}
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示例
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配置文件
application.yml
person:
enabled: true
name: 瓜田李下
age: 20
student:
name: 瓜田李下2
age: 20
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pojo 层
Person
@Data
@Component
@ConditionalOnProperty(prefix = "person",value = {"enabled"},havingValue = "true")
@ConfigurationProperties("person")
public class Person {
private String name;
private Integer age;
}
Student
@Data
@Component
@ConfigurationProperties(prefix = "student")
@ConditionalOnProperty(prefix = "student",value = "enabled",matchIfMissing = true)
public class Student {
private String name;
private Integer age;
}
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controller 层
HelloController
@RestController
public class HelloController {
@Resource
private Person person;
@Resource
private Student student;
@RequestMapping("/hello")
public String hello(){
System.out.println(person);
System.out.println(student);
return "success";
}
}
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使用测试
localhost:8080/hello
2020-07-06 18:27:20.222 INFO 19064 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet : Initializing Servlet 'dispatcherServlet'
2020-07-06 18:27:20.228 INFO 19064 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet : Completed initialization in 6 ms
Person(name=瓜田李下, age=20)
Student(name=瓜田李下2, age=20)
本文地址：https://blog.csdn.net/weixin_43931625/article/details/107140919
