Spring boot獲取yml字段內容為null的各種情況

首先，在resource目錄下配置test.yml文件

A:
  B: http://123.com?
  C: username="lili"&password="123456"
  D: username="lisa"&password="123456"

1.為了調用方便，將參數全部設置為static，結果可想而知，獲取不到，只能是null

package com.example.demo.constants;
import org.springframework.beans.factory.annotation.Value;
 import org.springframework.stereotype.Component;
@Component
 public class TestYml {
 public static String B;
 public static String C;
 public static String D;
</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span><span style="color: #000000;"> String getB() {
    </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> B;
}
@Value(</span>"${A.B}"<span style="color: #000000;">)
</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> setB(String b) {
    B </span>=<span style="color: #000000;"> b;
}

</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span><span style="color: #000000;"> String getC() {
    </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> C;
}
@Value(</span>"${A.C}"<span style="color: #000000;">)
</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> setC(String c) {
    C </span>=<span style="color: #000000;"> c;
}

</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span><span style="color: #000000;"> String getD() {
    </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> D;
}
@Value(</span>"${A.D}"<span style="color: #000000;">)
</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> setD(String d) {
    D </span>=<span style="color: #000000;"> d;
}

}

執行測試代碼

@RunWith(SpringRunner.class)
@SpringBootTest(classes = Application.class)
public class ApplicationTests {
    @Test
    public void test(){
        String b = TestYml.B;
        System.out.println(b);
    }
}

得到結果如下：

2.然后去掉set方法中的static，執行上一步的測試代碼可以正常獲取

 

3.如果需要將B分別和C，D進行拼接呢，將代碼修改如下：

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
@Component
 public class TestYml {
 public static String B;
 public static String C;
 public static String D;
</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span><span style="color: #000000;"> String getB() {
    </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> B;
}
@Value(</span>"${A.B}"<span style="color: #000000;">)
</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> setB(String b) {
    B </span>=<span style="color: #000000;"> b;
}

</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span><span style="color: #000000;"> String getC() {
    </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> C;
}
@Value(</span>"${A.C}"<span style="color: #000000;">)
</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> setC(String c) {
    C </span>= getB() +<span style="color: #000000;"> c;
}

</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span><span style="color: #000000;"> String getD() {
    </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> D;
}
@Value(</span>"${A.D}"<span style="color: #000000;">)
</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> setD(String d) {
    D </span>= getB() +<span style="color: #000000;">  d;
}

}

執行代碼如下：

@RunWith(SpringRunner.class)
@SpringBootTest(classes = Application.class)
public class ApplicationTests {
    @Test
    public void test(){
        String b = TestYml.B;
        String c = TestYml.C;
        String d = TestYml.D;
        System.out.println(b);
        System.out.println(c);
        System.out.println(d);
    }
}

拼接的結果時而正常，時而為null，如下：

4.然后將get方法的static也去掉，結果同樣也是不穩定

測試代碼如下：

@RunWith(SpringRunner.class)
@SpringBootTest(classes = Application.class)
public class ApplicationTests {
    @Test
    public void test(){
        int i = 10;
        for (int i1 = 0; i1 < i; i1++) {
            String b = TestYml.B;
            String c = TestYml.C;
            String d = TestYml.D;
            System.out.println(b);
            System.out.println(c);
            System.out.println(d);
        }
    }
}

結果如下：

5.將@Value至於參數處，且將參數的static也去掉，並且將測試代碼改為注入的方式，結果則是拼接的null都不見了

 

6.然后修改get方法，將拼接的值get作為該參數的返回，調用方式直接使用注入和get方法，獲取值才正常

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
@Component
 public class TestYml {
 @Value("${A.B}")
 private String B;
 @Value("${A.C}")
 private String C;
 @Value("${A.D}")
 private String D;
</span><span style="color: #0000ff;">public</span><span style="color: #000000;"> String getB() {
    </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> B;
}

</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> setB(String b) {
    B </span>=<span style="color: #000000;"> b;
}

</span><span style="color: #0000ff;">public</span><span style="color: #000000;"> String getC() {
    </span><span style="color: #0000ff;">return</span> getB() +<span style="color: #000000;"> C;
}

</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> setC(String c) {
    C </span>=<span style="color: #000000;"> c;
}

</span><span style="color: #0000ff;">public</span><span style="color: #000000;"> String getD() {
    </span><span style="color: #0000ff;">return</span> getB() +<span style="color: #000000;"> D;
}

</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> setD(String d) {
    D </span>=<span style="color: #000000;"> d;
}

}

測試代碼

@RunWith(SpringRunner.class)
@SpringBootTest(classes = Application.class)
public class ApplicationTests {
    @Autowired
    TestYml testYml;
    @Test
    public void test(){
        int i = 10;
        for (int i1 = 0; i1 < i; i1++) {
            String b = testYml.getB();
            String c = testYml.getC();
            String d = testYml.getD();
            System.out.println(b);
            System.out.println(c);
            System.out.println(d);
        }
    }
}

執行結果可以正常獲取到值

原文地址：https://www.cnblogs.com/biyuting/p/11184254.html