java 加载properties配置文件属性到常量

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public class CustomizedPropertyPlaceholderConfigurer extends PropertyPlaceholderConfigurer{

/**
* 属性前缀，可以使用表达式${}。如果使用表达式，表示从属性文件中的字段读取。
* 如果为空，表示不使用前缀。
*/
private String prefix;

/**
* 需要注入的常量类名数组
*/
private String[] configureClasses;

@SuppressWarnings("unchecked")
protected void processProperties(ConfigurableListableBeanFactory beanFactoryToProcess, Properties props)
throws BeansException {
super.processProperties(beanFactoryToProcess, props);

if (configureClasses == null){
return;
}


String prefixValue = null;
if (prefix != null && !prefix.isEmpty()){
// 如果前缀是表达式，需要从属性中读取
Pattern p = Pattern.compile("\\$\\{(.*)\\}");
Matcher matcher = p.matcher(prefix);
prefixValue = prefix;
if (matcher.find()) {
String prefixKey = matcher.group(1);
prefixValue = props.getProperty(prefixKey);
}
}

// 遍历多个常量类
for (int i = 0; i < configureClasses.length; i++) {
Class c = null;
try {
c = Class.forName(configureClasses[i]);
} catch (ClassNotFoundException e) {
e.printStackTrace();
continue;
}

Field[] fields = c.getFields();

// 遍历属性列表，注入到常量字段中
for (Enumeration<?> k = props.propertyNames(); k.hasMoreElements();) {
String key = (String) k.nextElement();

// 遍历常量字段数组，找到与属性对应的常量字段
for (int j = 0; fields != null && j < fields.length; j++) {
// 取出字段名称，如果有前缀，需要加上前缀
String keyStr = fields[j].getName();
if (prefixValue != null && !prefixValue.isEmpty())
keyStr = prefixValue + "." + fields[j].getName();

// 判断常量字段是否有属性匹配，不区分大小写。
if (keyStr.equalsIgnoreCase(key)) {
// 从属性中取出字段值，并存到字段中
String value = props.getProperty(key);
if (value != null) {
value = value.trim();
try {
if (Integer.TYPE.equals(fields[j].getType())) {
fields[j].setInt(null, Integer.parseInt(value));
} else if (Long.TYPE.equals(fields[j].getType())) {
fields[j].setLong(null, Long.parseLong(value));
} else if (Short.TYPE.equals(fields[j].getType())) {
fields[j].setShort(null, Short.parseShort(value));
} else if (Double.TYPE.equals(fields[j].getType())) {
fields[j].setDouble(null, Double.parseDouble(value));
} else if (Float.TYPE.equals(fields[j].getType())) {
fields[j].setFloat(null, Float.parseFloat(value));
} else if (Boolean.TYPE.equals(fields[j].getType())) {
fields[j].setBoolean(null, Boolean.parseBoolean(value));
} else {
fields[j].set(null, value);
}
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}

}
break;
}
}
}
}

}

public String getPrefix() {
return prefix;
}

public void setPrefix(String prefix) {
this.prefix = prefix;
}

public String[] getConfigureClasses() {
return configureClasses;
}

public void setConfigureClasses(String[] configureClasses) {
this.configureClasses = (configureClasses != null)? configureClasses.clone() : null;
}

public void setConfigureClass(String configureClass) {
this.configureClasses = new String[] {configureClass};

}

2 常量类用户接收配置文件信息

/**
* @ClassName: ConfigConstants
* @Description: 配置文件赋值常量类
* @author A18ccms a18ccms_gmail_com
* @date 2016-9-27 下午4:19:02
*
*/
public class ConfigConstants {

/**
* jdbc.properties
*/
public static String URL = "";

public static String DRIVER = "";

public static String USERNAME = "";

public static String PASSWORD = "";

/**
* redis_cache.properties
*/
public static int MAXIdle = 0;

public static int MAXTotal = 0;

public static int maxWaitMillis = 0;

public static boolean testOnBorrow = false;

public static String redisMasterIP = "";

public static int redisMasterPort = 0;

public static String redisSlaveIP = "";

public static String redisSlavePort = "";

/**
* application.properties
*/
public static String ACCOUNT = "";

public static String PSWD = "";

public static String POST_URL = "";

public static String USER_SALT = "";

public static String CONTEXT_NAME = "";

public static String MERCHANT_ID = "";

public static String REAPAL_KEY = "";

public static String SELLER_EMAIL = "";

public static String PRIVATE_KEY_PASSWORD = "";

public static String APP_DOMAIN_NAME = "";

public static String CERT_PATH = "" ;

}

3，配置文件信息

<bean id="property"
class="com.wtjr.common.util.CustomizedPropertyPlaceholderConfigurer">
<property name="locations">
<list>
<value>classpath:jdbc.properties</value>
<value>classpath:redis_cache.properties</value>
<value>classpath:application.properties</value>
</list>
</property>
<property name="configureClasses">
<list>
<value>com.wtjr.common.constant.ConfigConstants</value>
</list>
</property>
</bean>

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