我创建了一个名为“文件夹”的Java bean（暂时只是很简单，因为我现在想使它大部分都能工作），我将其导出为.jar文件并将其放置在/ WEB-INF /
lib /中。目录。但是，当我尝试在预期的页面上使用它时，出现此错误（如果需要，我可以添加long语句的res）：

Feb 22, 2013 12:02:31 PM org.apache.catalina.core.ApplicationDispatcher invoke
SEVERE: Servlet.service() for servlet jsp threw exception
java.lang.UnsupportedClassVersionError: com/mysite/folders/Folders : Unsupported major.minor     version 51.0 (unable to load class com.mysite.folders.Folders)

如果可能是导致问题的原因，请使用以下bean：

package com.mysite.folders;

import java.io.Serializable;
import java.util.ArrayList;

public class Folders implements Serializable {

private String accountNumber;
private String folderName;
private String groupName;
private ArrayList<String> folderNames;
private ArrayList<String> groupNames;

public String getAccountNumber() {
    return accountNumber;
}

public void setAccountNumber(String accountNumber) {
    this.accountNumber = accountNumber;
}

public String getFolderName() {
    return folderName;
}

public void setFolderName(String folderName) {
    this.folderName = folderName;
}

public String getGroupName() {
    return groupName;
}

public void setGroupName(String groupName) {
    this.groupName = groupName;
}

public ArrayList<String> getFolderNames() {
    return folderNames;
}

public void setFolderNames(ArrayList<String> folderNames) {
    this.folderNames = folderNames;
}

public ArrayList<String> getGroupNames() {
    return groupNames;
}

public void setGroupNames(ArrayList<String> groupNames) {
    this.groupNames = groupNames;
}

public Folders(String accountNumber, String folderName, String groupName,
        ArrayList<String> folderNames, ArrayList<String> groupNames) {
    super();
    this.accountNumber = accountNumber;
    this.folderName = folderName;
    this.groupName = groupName;
    this.folderNames = folderNames;
    this.groupNames = groupNames;
}
}

最后是我在页面上的声明：

<jsp:useBean id="Folders" scope="session" class="com.mysite.folders.Folders" />

我觉得我做得很好，并且不确定为什么这行不通。任何建议或技巧将不胜感激。