随机端口
我们知道为spring boot配置随机端口非常简单，有两种办法：
- 设置端口为0
server.port=0
eureka.instance.instance-id=${spring.application.name}-${spring.cloud.client.ipAddress}:${random.int}
- 设置端口为随机值
server.port=${random.int[1000,1999]}
问题
我们无论使用上述的哪种办法，都会存在一些问题，有且不限于如下：
- eureka界面上的Status无法显示真实的端口
- 点击Status列的链接会跳转到错误的端口
- 如果使用了
LoadBalancerInterceptor会导致连接异常，原因也是导向了错误的端口 - ...
解决思路
不难发现问题的根本就是每个地方都会再调用一次random.int生成不同的随机数，如果新生成的随机数被赋予端口意义使用，那么会因为这个数和真实端口并不一致导致发生异常。
random.int 是springboot默认提供的，我想实现一个自己的random.int，只赋值一次即可，往后再调用便返回已生成的值。
解决方法
random.int 是springboot默认提供的，
Ctrl+Click发现实现类是RandomValuePropertySource.我尝试把
server.port=${random.int[1000,2000]}改成server.port=${randomServerPort.value[1000,2000]}（${randomServerPort.value[1000,2000]}是我们要自定义的），运行后得到异常的堆栈信息
Caused by: java.lang.IllegalArgumentException: Could not resolve placeholder 'randomServerPort.value[1000,2000]' in value "${randomServerPort.value[1000,2000]}"
at org.springframework.util.PropertyPlaceholderHelper.parseStringValue(PropertyPlaceholderHelper.java:174) ~[spring-core-4.3.14.RELEASE.jar:4.3.14.RELEASE]
at org.springframework.util.PropertyPlaceholderHelper.replacePlaceholders(PropertyPlaceholderHelper.java:126) ~[spring-core-4.3.14.RELEASE.jar:4.3.14.RELEASE]
at org.springframework.core.env.AbstractPropertyResolver.doResolvePlaceholders(AbstractPropertyResolver.java:236) ~[spring-core-4.3.14.RELEASE.jar:4.3.14.RELEASE]
at org.springframework.core.env.AbstractPropertyResolver.resolveRequiredPlaceholders(AbstractPropertyResolver.java:210) ~[spring-core-4.3.14.RELEASE.jar:4.3.14.RELEASE]
at org.springframework.core.env.AbstractPropertyResolver.resolveNestedPlaceholders(AbstractPropertyResolver.java:227) ~[spring-core-4.3.14.RELEASE.jar:4.3.14.RELEASE]
at org.springframework.core.env.PropertySourcesPropertyResolver.getProperty(PropertySourcesPropertyResolver.java:84) ~[spring-core-4.3.14.RELEASE.jar:4.3.14.RELEASE]
at org.springframework.core.env.PropertySourcesPropertyResolver.getProperty(PropertySourcesPropertyResolver.java:66) ~[spring-core-4.3.14.RELEASE.jar:4.3.14.RELEASE]
at org.springframework.core.env.AbstractEnvironment.getProperty(AbstractEnvironment.java:537) ~[spring-core-4.3.14.RELEASE.jar:4.3.14.RELEASE]
at org.springframework.boot.bind.RelaxedPropertyResolver.getProperty(RelaxedPropertyResolver.java:84) ~[spring-boot-1.5.10.RELEASE.jar:1.5.10.RELEASE]
at org.springframework.boot.bind.RelaxedPropertyResolver.getProperty(RelaxedPropertyResolver.java:74) ~[spring-boot-1.5.10.RELEASE.jar:1.5.10.RELEASE]
at org.springframework.boot.actuate.autoconfigure.EndpointWebMvcAutoConfiguration$ManagementServerPort.getPortProperty(EndpointWebMvcAutoConfiguration.java:409) ~[spring-boot-actuator-1.5.10.RELEASE.jar:1.5.10.RELEASE]
at org.springframework.boot.actuate.autoconfigure.EndpointWebMvcAutoConfiguration$ManagementServerPort.get(EndpointWebMvcAutoConfiguration.java:361) ~[spring-boot-actuator-1.5.10.RELEASE.jar:1.5.10.RELEASE]
at org.springframework.boot.actuate.autoconfigure.EndpointWebMvcAutoConfiguration$OnManagementMvcCondition.getMatchOutcome(EndpointWebMvcAutoConfiguration.java:345) ~[spring-boot-actuator-1.5.10.RELEASE.jar:1.5.10.RELEASE]
at org.springframework.boot.autoconfigure.condition.SpringBootCondition.matches(SpringBootCondition.java:47) ~[spring-boot-autoconfigure-1.5.10.RELEASE.jar:1.5.10.RELEASE]
... 16 more
-
从堆栈信息中找到解析的类
PropertyPlaceholderHelper，打上断点
-
跳转到
PropertySourcesPropertyResolver，找到了真正的解析器propertySources
我们只要自己写一个
PropertySource，然后放进去就可以了。照着RandomValuePropertySource写一个自己的
import lombok.extern.slf4j.Slf4j;
import org.springframework.core.env.PropertySource;
import org.springframework.util.StringUtils;
@Slf4j
public class RandomServerPortPropertySource extends PropertySource {
/**
* Name of the random {@link PropertySource}.
*/
public static final String RANDOM_SERVER_PORT_PROPERTY_SOURCE_NAME = "randomServerPort";
private static final String PREFIX = "randomServerPort.";
public RandomServerPortPropertySource(String name) {
super(name, new RandomServerPort());
}
public RandomServerPortPropertySource() {
this(RANDOM_SERVER_PORT_PROPERTY_SOURCE_NAME);
}
public RandomServerPortPropertySource(String name, RandomServerPort source) {
super(name, source);
}
@Override
public Object getProperty(String name) {
if (!name.startsWith(PREFIX)) {
return null;
}
if (log.isTraceEnabled()) {
log.trace("Generating randomServerPort property for '" + name + "'");
}
return getRandomServerPortValue(name.substring(PREFIX.length()));
}
private Object getRandomServerPortValue(String type) {
String range = getRange(type, "value");
if (range != null) {
return getNextValueInRange(range);
}
return null;
}
private String getRange(String type, String prefix) {
if (type.startsWith(prefix)) {
int startIndex = prefix.length() + 1;
if (type.length() > startIndex) {
return type.substring(startIndex, type.length() - 1);
}
}
return null;
}
private int getNextValueInRange(String range) {
String[] tokens = StringUtils.commaDelimitedListToStringArray(range);
int start = Integer.parseInt(tokens[0]);
if (tokens.length == 1) {
return getSource().nextValue(start);
}
return getSource().nextValue(start, Integer.parseInt(tokens[1]));
}
}
import org.apache.commons.lang3.RandomUtils;
/**
* 随机生成一个端口，并只生成一次
*/
public class RandomServerPort {
private int serverPort;
private final int start = 0;
private final int end = 65535;
public int nextValue(int start) {
return nextValue(start, end);
}
public int nextValue(int start, int end) {
start = start < this.start? this.start: start;
end = end > this.end? this.end: end;
if (serverPort == 0){
synchronized (this){
if (serverPort == 0){
serverPort = RandomUtils.nextInt(start, end);
}
}
}
return serverPort;
}
}
- 这种解析器是解析
application.properties的，所以需要很早就加载上去，不难想到用ApplicationListener
import org.springframework.boot.context.event.ApplicationEnvironmentPreparedEvent;
import org.springframework.context.ApplicationListener;
public class MyApplicationEnvironmentPreparedEventListener implements ApplicationListener {
@Override
public void onApplicationEvent(ApplicationEnvironmentPreparedEvent event) {
event.getEnvironment().getPropertySources().addLast(new RandomServerPortPropertySource());
}
}
- 添加监听器
@SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication app = new SpringApplication(Application.class);
app.addListeners(new MyApplicationEnvironmentPreparedEventListener());
app.run(args);
}
}
- 配置文件修改一下
server.port=${randomServerPort.value[1000,2000]}
eureka.instance.instance-id=${spring.application.name}-${spring.cloud.client.ipAddress}:${randomServerPort.value[1000,2000]}
# 省略...
-
结果如下
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