SpringBoot 讀取yml檔案,以及獲取不到value的情況
阿新 • • 發佈:2019-01-24
如果出現value無法獲取的情況,請看一下pom專案是不是依賴不對,
一,spring元件重寫構造方法,在構造方法中引用@value為null
由於spring例項化順序為先執行構造方法,再注入成員變數,所以序為先執行構造方法,再注入成員變數,所以ing例項化順取值為null
解決辦法為:再寫一個常量類,在常量類中引用@value,再在構造方法中引用常量類的變數即可。
二,呼叫spring元件時使用new物件,而不是@Autowired
三,使用final或static修飾成員變數
四,spring mvc中引用@value為null
spring mvc是spring的子容器,需要在兩個配置檔案中都匯入配置檔案
<context:property-placeholder location="classpath:jdbc.properties" ignore-unresolvable="true"/>
在spring boot中,簡單幾步,讀取配置檔案(application.yml)中各種不同型別的屬性值:
1、引入依賴:
<!-- 支援 @ConfigurationProperties 註解 --> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-configuration-processor</artifactId> <optional>true</optional> </dependency>
2、配置檔案(application.yml)中配置各個屬性的值
myProps: #自定義的屬性和值 simpleProp: simplePropValue arrayProps: 1,2,3,4,5 listProp1: - name: abc value: abcValue - name: efg value: efgValue listProp2: - config2Value1 - config2Vavlue2 mapProps: key1: value1 key2: value2
3、建立一個bean來接收配置資訊:
@Component
@ConfigurationProperties(prefix="myProps") //接收application.yml中的myProps下面的屬性
public class MyProps {
private String simpleProp;
private String[] arrayProps;
private List<Map<String, String>> listProp1 = new ArrayList<>(); //接收prop1裡面的屬性值
private List<String> listProp2 = new ArrayList<>(); //接收prop2裡面的屬性值
private Map<String, String> mapProps = new HashMap<>(); //接收prop1裡面的屬性值
public String getSimpleProp() {
return simpleProp;
}
//String型別的一定需要setter來接收屬性值;maps, collections, 和 arrays 不需要
public void setSimpleProp(String simpleProp) {
this.simpleProp = simpleProp;
}
public List<Map<String, String>> getListProp1() {
return listProp1;
}
public List<String> getListProp2() {
return listProp2;
}
public String[] getArrayProps() {
return arrayProps;
}
public void setArrayProps(String[] arrayProps) {
this.arrayProps = arrayProps;
}
public Map<String, String> getMapProps() {
return mapProps;
}
public void setMapProps(Map<String, String> mapProps) {
this.mapProps = mapProps;
}
}
啟動後,這個bean裡面的屬性就會自動接收配置的值了。
4、單元測試用例:
@Autowired
private MyProps myProps;
@Test
public void propsTest() throws JsonProcessingException {
System.out.println("simpleProp: " + myProps.getSimpleProp());
System.out.println("arrayProps: " + objectMapper.writeValueAsString(myProps.getArrayProps()));
System.out.println("listProp1: " + objectMapper.writeValueAsString(myProps.getListProp1()));
System.out.println("listProp2: " + objectMapper.writeValueAsString(myProps.getListProp2()));
System.out.println("mapProps: " + objectMapper.writeValueAsString(myProps.getMapProps()));
}
測試結果:
simpleProp: simplePropValue
arrayProps: ["1","2","3","4","5"]
listProp1: [{"name":"abc","value":"abcValue"},{"name":"efg","value":"efgValue"}]
listProp2: ["config2Value1","config2Vavlue2"]
mapProps: {"key1":"value1","key2":"value2"}