Spring boot获取yml字段内容为null的各种情况

首先，在resource目录下配置test.yml文件

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

1.为了调用方便，将参数全部设置为static，结果可想而知，获取不到，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;
}

}

执行测试代码

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

得到结果如下：

2.然后去掉set方法中的static，执行上一步的测试代码可以正常获取

3.如果需要将B分别和C，D进行拼接呢，将代码修改如下：

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;
}

}

执行代码如下：

@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);
    }
}

拼接的结果时而正常，时而为null，如下：

4.然后将get方法的static也去掉，结果同样也是不稳定

测试代码如下：

@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);
        }
    }
}

结果如下：

5.将@Value至于参数处，且将参数的static也去掉，并且将测试代码改为注入的方式，结果则是拼接的null都不见了

6.然后修改get方法，将拼接的值get作为该参数的返回，调用方式直接使用注入和get方法，获取值才正常

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Component
public class TestYml {
@Value("$")
private String B;
@Value("$")
private String C;
@Value("$")
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;
}

}

测试代码

@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);
        }
    }
}

执行结果可以正常获取到值

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