如何通过托管Bean在类中设置属性?

我想通过faces配置文件在java类中设置一个属性:

<managed-bean>
    <managed-bean-name>utilsBean</managed-bean-name>
    <managed-bean-class>org.acme.bank.app.UtilsBean</managed-bean-class>
    <managed-bean-scope>session</managed-bean-scope>
    <managed-property>
      <property-name>filePath</property-name>
      <value>#{javascript:@ReplaceSubstring(@LeftBack(database.getFilePath(),"\\"),"\\","/")+"/"}</value>
    </managed-property>
  </managed-bean>

在我的UtilsBean类上,我有一个as属性:

public String filePath;

和

public String getFilePath() {
        return filePath;
    }

    public void setFilePath(String filePath) {
        this.filePath = filePath;
    }

但是当我在构造函数中输出值时,我得到一个空值。

public UtilsBean() throws Exception {
        super();        
        Database database = ExtLibUtil.getCurrentDatabase();
        System.out.println("database.getFilePath() = " + database.getFilePath());//returns filepath of current nsf
        System.out.println("this filepath = " + this.filePath);//returns null


        try {
        ...
    }
}

在我看来,该属性不是通过faces配置设置的,还是我做得不对?