如何解决The method getId() is undefined for the type String问题 java web问题
（1）package com.share.ORM;

import com.share.ORM.NewsColumns;

/**
* NewsColumns entity. @author MyEclipse Persistence Tools
*/

public class NewsColumns implements java.io.Serializable {

// Fields

private Integer id;
private Integer parentId;
private String columnCode;
private String columnName;
private NewsColumns newsColumns;
private String NewsColumns;

// Constructors

/** default constructor */
public NewsColumns() {
}

/** full constructor */
public NewsColumns(Integer parentId, String columnCode, String columnName) {
this.parentId = parentId;
this.columnCode = columnCode;
this.columnName = columnName;
}

// Property accessors

public Integer getId() {
return this.id;
}

public void setId(Integer id) {
this.id = id;
}

public Integer getParentId() {
return this.parentId;
}

public void setParentId(Integer parentId) {
this.parentId = parentId;
}

public String getColumnCode() {
return this.columnCode;
}

public void setColumnCode(String columnCode) {
this.columnCode = columnCode;
}

public String getColumnName() {
return this.columnName;
}

public void setColumnName(String columnName) {
this.columnName = columnName;
}
public void setNewscolumns(NewsColumns newscolumns) {
this.setNewsColumns(newscolumns);
}

public String getNewsColumns() {
// TODO Auto-generated method stub
return this.NewsColumns;
}

public void setNewsColumns(NewsColumns newsColumns) {
this.newsColumns = newsColumns;
}

}


（2）package com.share.action;

import java.io.UnsupportedEncodingException;
import java.util.List;
import com.share.ORM.NewsColumns;
import com.share.service.ColumnsService;
import com.opensymphony.xwork2.ActionSupport;
import com.opensymphony.xwork2.ModelDriven;

/** 新闻栏目管理控制器 */
@SuppressWarnings("serial")
public class ColumnsAction extends ActionSupport implements ModelDriven<NewsColumns>{
/** 通过依赖注入ColumnsService组件实例 */
ColumnsService service;

/** 新闻栏目管理所有请求中常用的参数值 */
private String actionMsg;//Action间传递的消息参数
private List<NewsColumns> columnsList;//新闻栏目列表
private String parentid;//上级栏目的ID

//采用模型驱动
private NewsColumns model=new NewsColumns();//用于封装新闻栏目属性的模型实例
public NewsColumns getModel() {
return model;
}

/** 处理浏览新闻栏目请求 */
public String browseColumns(){
if(actionMsg!=null){
try {
actionMsg = new String(actionMsg.getBytes("ISO8859-1"),"gbk");
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
addActionMessage(actionMsg);
}
columnsList = service.browseColumns();//调用业务逻辑组件取得新闻栏目列表
return SUCCESS;
}

/** 处理新增新闻栏目请求 */
public String addColumns(){
NewsColumns tempColumns = new NewsColumns();
tempColumns.setColumnName(model.getColumnName());
tempColumns.setColumnCode(model.getColumnCode());
if(parentid!=null && Integer.parseInt(parentid)>0){
tempColumns.setNewscolumns(service.loadColumns(Integer.valueOf(parentid)));
}
if (service.saveOrUpdateColumns(tempColumns)){//调用业务逻辑组件保存新增的新闻栏目
addActionMessage(getText("columns_add_succ"));
}else{
addActionMessage(getText("columns_add_fail"));
}
return SUCCESS;
}

/** 处理删除新闻栏目请求 */
public String delColumns(){
if (model.getId()!=null){
if (service.delColumns(model.getId())){//调用业务逻辑组件删除指定的新闻栏目

actionMsg = getText("columns_del_succ");
}else{
actionMsg = getText("columns_del_fail");
}
}else{
actionMsg = getText("columns_del_fail");
}
return "toBrowseColumns";
}

/** 处理查看新闻栏目请求 */
public String viewColumns(){
if (model.getId()!=null){
//调用业务逻辑组件装载指定的新闻栏目
NewsColumns tempColumns = service.loadColumns(model.getId());
if (tempColumns!=null){
model.setColumnName(tempColumns.getColumnName().trim());
model.setColumnCode(tempColumns.getColumnCode().trim());
if (tempColumns.getNewsColumns()!=null){
parentid = tempColumns.getNewsColumns().getId().toString();
}else{
parentid = "-1";
}
return SUCCESS;
}else{
actionMsg = getText("columns_view_fail");
return "toBrowseColumns";
}
}else{
actionMsg = getText("columns_view_fail");
return "toBrowseColumns";
}
}

/** 处理装载新闻栏目请求 */
public String editColumns(){
if (model.getId()!=null){
//调用业务逻辑组件装载指定的新闻栏目
NewsColumns tempColumns = service.loadColumns(model.getId());
if (tempColumns!=null){
model.setColumnName(tempColumns.getColumnName().trim());
model.setColumnCode(tempColumns.getColumnCode().trim());
if (tempColumns.getNewsColumns()!=null){
parentid = tempColumns.getNewsColumns().getId().toString();
}else{
parentid = "-1";
}
return SUCCESS;
}else{
actionMsg = getText("columns_edit_fail");
return "toBrowseColumns";
}
}else{
actionMsg = getText("columns_edit_fail");
return "toBrowseColumns";
}
}

/** 处理更新新闻栏目请求 */
public String updateColumns(){
NewsColumns tempColumns = service.loadColumns(model.getId());
tempColumns.setColumnName(model.getColumnName());
tempColumns.setColumnCode(model.getColumnCode());
if(parentid!=null && Integer.parseInt(parentid)>0){
tempColumns.setNewscolumns(service.loadColumns(Integer.valueOf(parentid)));
}else{
tempColumns.setNewscolumns(null);
}
if (service.saveOrUpdateColumns(tempColumns)){//调用业务逻辑组件更新指定的新闻栏目
addActionMessage(getText("columns_edit_succ"));
}else{
addActionMessage(getText("columns_edit_fail"));
}
return INPUT;
}

/** 处理一级新闻栏目下拉列表请求 */
public String listColumns(){
columnsList = service.listColumns();//调用业务逻辑组件取得一级新闻栏目列表
NewsColumns firstnode = new NewsColumns();
firstnode.setId(-1);
firstnode.setColumnName("无上级栏目");
columnsList.add(0,firstnode);
return SUCCESS;
}

public String getActionMsg() {
return actionMsg;
}
public void setActionMsg(String actionMsg) {
this.actionMsg = actionMsg;
}
public ColumnsService getService() {
return service;
}
public void setService(ColumnsService service) {
this.service = service;
}

public List<NewsColumns> getColumnsList() {
return columnsList;
}
public void setColumnsList(List<NewsColumns> columnsList) {
this.columnsList = columnsList;
}

public String getParentid() {
return parentid;
}

public void setParentid(String parentid) {
this.parentid = parentid;
}
}


[解决办法]
对象是不是引用错了 该括号的括号起来 再.getId()