读取tomcat配置文件

applicationContext.xml

<bean class="com.tydic.dep.common.util.props.PropertyPlaceholderConfigurer">
    <property name="locations">
        <list>
            <value>file:///${catalina.home}/conf/depBssCloudCenter.xml</value>
        </list>
    </property>
    <property name="fileEncoding" value="UTF-8"/>
    <property name="ignoreUnresolvablePlaceholders" value="true"/>
</bean>

Demo.java

public class ConfigUtils {
    public static String getGroupId() {
        String property = SystemProperties.getProperty("dep.bss.cloud.groupId");
        if (ObjectIsNull.check(property)) {
            throw new RuntimeException("groupId 未在tomcat配置文件中配置");
        }
        return property;
    }
}

PropertyPlaceholderConfigurer.java

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.core.io.Resource;
import org.springframework.util.DefaultPropertiesPersister;
import org.springframework.util.PropertiesPersister;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.Iterator;
import java.util.Map;
import java.util.Properties;
import java.util.Set;

/**
 * 外部配置文件加载类
 *
 * @author chengyq
 * @version V1.0
 * @date 2022/4/29 16:27
 */
public class PropertyPlaceholderConfigurer extends org.springframework.beans.factory.config.PropertyPlaceholderConfigurer {
    static Logger logger = LoggerFactory.getLogger(PropertyPlaceholderConfigurer.class);
    private Resource[] locations;
    private String fileEncoding;
    private boolean ignoreResourceNotFound = false;
    private Properties props;

    public PropertyPlaceholderConfigurer() {
    }

    public Properties getProperties() {
        return this.props;
    }

    public String getProperty(String key) {
        return this.props != null ? this.props.getProperty(key) : null;
    }

    @Override
    public void setLocations(Resource[] locations) {
        this.locations = locations;
    }

    @Override
    public void loadProperties(Properties props) throws IOException {
        if (this.locations != null) {
            PropertiesPersister propertiesPersister = new DefaultPropertiesPersister();

            for(int i = 0; i < this.locations.length; ++i) {
                Resource location = this.locations[i];
                if (logger.isDebugEnabled()) {
                    logger.debug("Loading properties file from " + location);
                }

                InputStream is = null;

                try {
                    is = location.getInputStream();
                    if (location.getFilename().endsWith(".xml")) {
                        propertiesPersister.loadFromXml(props, is);
                    } else if (this.fileEncoding != null) {
                        propertiesPersister.load(props, new InputStreamReader(is, this.fileEncoding));
                    } else {
                        propertiesPersister.load(props, is);
                    }

                    Properties properties = System.getProperties();
                    Set<Map.Entry<Object, Object>> entries = properties.entrySet();
                    Iterator<Map.Entry<Object, Object>> it = entries.iterator();

                    while(it.hasNext()) {
                        Map.Entry entry = it.next();
                        if (!props.containsKey(entry.getKey())) {
                            props.put(entry.getKey().toString(), entry.getValue());
                        }
                    }
                    this.props = props;
                    new PropertyPlaceholderConfigurer.SystemPropertiesImpl(props);
                    System.out.println("System env parameter:");
                    System.out.println("###############################################################################################");
                    System.out.println(props);
                    System.out.println("###############################################################################################");
                } catch (IOException var13) {
                    if (!this.ignoreResourceNotFound) {
                        throw var13;
                    }

                    logger.warn("Could not load properties from " + location + ": " + var13.getMessage());
                } finally {
                    if (is != null) {
                        is.close();
                    }

                }
            }
        }

    }

    public Resource[] getLocations() {
        return this.locations;
    }

    @Override
    public void setFileEncoding(String fileEncoding) {
        this.fileEncoding = fileEncoding;
    }

    @Override
    public void setIgnoreResourceNotFound(boolean ignoreResourceNotFound) {
        this.ignoreResourceNotFound = ignoreResourceNotFound;
    }

    static class SystemPropertiesImpl extends SystemProperties {
        Properties properties;

        public SystemPropertiesImpl(Properties properties) {
            this.properties = properties;
            this.initialize(this);
        }

        @Override
        public Properties getProperties() {
            return this.properties;
        }
    }
    
}

SystemProperties.java

import java.util.Properties;

/**
 * 加载配置
 *
 * @author chengyq
 * @version V1.0
 * @date 2022/4/29 16:30
 */
public abstract class SystemProperties {
    private static SystemProperties INSTANCE;
    private static final String ERROR_MSG = SystemProperties.class.getName() + " already existed.";

    public SystemProperties() {
    }

    public static SystemProperties getInstance() {
        if (INSTANCE == null) {
            throw new RuntimeException("没有初始化SystemProperties");
        } else {
            return INSTANCE;
        }
    }

    public static String getProperty(String key) {
        return getInstance().getProperties().getProperty(key);
    }

    /**
     * 返回全量的配置
     * @return 
     */
    public abstract Properties getProperties();

    public void initialize(SystemProperties systemProperties) {
        if (INSTANCE != null) {
            System.err.println(ERROR_MSG);
        }

        INSTANCE = systemProperties;
    }
}