这个问答的功能应该如何实现？

整个源码限于时间，等有空分享吧，先只说下db设计吧。

提问表已经解答过，请参考这个：最代码数据库设计，期待牛哥分析~大家快来学习啦~！

回答表结构如下：

CREATE TABLE `zuidaima_answer` (
  `id` bigint(20) unsigned NOT NULL auto_increment,
  `create_time` datetime NOT NULL,
  `update_time` datetime default NULL,
  `user_id` bigint(20) NOT NULL,
  `content` longtext NOT NULL,
  `extend_json` varchar(10000) default '',
  `target_id` bigint(20) NOT NULL COMMENT '项目id，或分享，或寻求',
  `is_perfect` int(2) NOT NULL default '0' COMMENT '是否是最完美回答，0否1是',
  `status` int(2) NOT NULL COMMENT '-1删除0待审核2正常',
  `publish_time` datetime default NULL,
  `first_sort` int(11) NOT NULL default '0',
  `second_sort` int(11) NOT NULL default '0',
  `third_sort` int(11) NOT NULL default '0',
  PRIMARY KEY  (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8

提问可以有多个回答。

java bean类如下：

Project.java

package com.zuidaima.core.module;

/**
 **@author www.zuidaima.com
 2013-06-13 23:23:35
 */
import java.util.Date;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Table;
import javax.persistence.Transient;

import net.sf.json.JSONObject;

import org.apache.commons.lang.builder.ToStringBuilder;
import org.apache.log4j.Logger;
import org.springframework.data.domain.Page;

import com.javaniu.core.constants.ModuleConstants;
import com.javaniu.core.util.StringUtil;

@Entity
@Table(name = "zuidaima_project")
public class Project extends BaseEntity {
	private static final Logger logger = Logger.getLogger(Project.class);
	private long userId = 0;
	private User user;
	private int type;
	private String title;
	private String content;
	private int status = ModuleConstants.MODULE_STATUS_VERIFING;
	private String extendJson;
	private JSONObject extend;
	private String topics;
	private long sourceId = 0;
	private BaseEntity source;
	private int firstSort;// view count sort
	private int secondSort;// download count sort
	private int thirdSort;// comment count sort
	private Page<Comment> comments;
	private Date publishTime;
	private String contentExt;
	private String contentExt2;
	private String contentExt3;
	private String fromUrl;
	private long uuid;
	private String tags;

	public Project() {
		this.createTime = new Date();
		this.updateTime = createTime;
	}

	@Column(name = "user_id")
	public long getUserId() {
		return this.userId;
	}

	public void setUserId(long userId) {
		this.userId = userId;
	}

	public int getType() {
		return this.type;
	}

	public void setType(int type) {
		this.type = type;
	}

	public String getTitle() {
		return this.title;
	}

	public void setTitle(String title) {
		this.title = title;
	}

	public String getContent() {
		return this.content;
	}

	public void setContent(String content) {
		this.content = content;
	}

	public int getStatus() {
		return this.status;
	}

	public void setStatus(int status) {
		this.status = status;
	}

	@Column(name = "extend_json")
	public String getExtendJson() {
		return this.extendJson;
	}

	public void setExtendJson(String extendJson) {
		this.extendJson = extendJson;
	}

	@Transient
	public JSONObject getExtend() {
		if (extendJson == null || extendJson.trim().equals("")) {
			extend = new JSONObject();
		} else {
			try {
				extend = JSONObject.fromObject(extendJson);
			} catch (Exception e) {
				logger.error("JSONObject.fromObject():" + e.getMessage()
						+ ",extendJson:" + extendJson);
				extend = new JSONObject();
			}
		}
		if (!extend
				.containsKey(ModuleConstants.PROJECT_EXTEND_JSON_ANSWER_COUNT)) {
			extend.put(ModuleConstants.PROJECT_EXTEND_JSON_ANSWER_COUNT, 0);
		}
		if (!extend.containsKey(ModuleConstants.PROJECT_EXTEND_JSON_NIUBI)) {
			extend.put(ModuleConstants.PROJECT_EXTEND_JSON_NIUBI,
					ModuleConstants.PROJECT_DEFAULT_NIUBI);
		}
		if (!extend
				.containsKey(ModuleConstants.PROJECT_EXTEND_JSON_COLLECT_COUNT)) {
			extend.put(ModuleConstants.PROJECT_EXTEND_JSON_COLLECT_COUNT, 0);
		}
		if (!extend.containsKey(ModuleConstants.PROJECT_EXTEND_IS_VALIDATED)) {
			extend.put(ModuleConstants.PROJECT_EXTEND_IS_VALIDATED, 0);
		}
		if (!extend.containsKey(ModuleConstants.PROJECT_EXTEND_IS_PERFECT)) {
			extend.put(ModuleConstants.PROJECT_EXTEND_IS_PERFECT, 0);
		}
		if (!extend.containsKey(ModuleConstants.PROJECT_EXTEND_IS_ORGINAL)) {
			extend.put(ModuleConstants.PROJECT_EXTEND_IS_ORGINAL, 0);
		}
		if (!extend.containsKey(ModuleConstants.PROJECT_EXTEND_IS_REORGANIZE)) {
			extend.put(ModuleConstants.PROJECT_EXTEND_IS_REORGANIZE, 1);
		}
		return extend;
	}

	public void setExtend(JSONObject extend) {
		this.extend = extend;
	}

	public String getTopics() {
		return this.topics;
	}

	public void setTopics(String topics) {
		this.topics = topics;
	}

	@Column(name = "source_id")
	public long getSourceId() {
		return this.sourceId;
	}

	public void setSourceId(long sourceId) {
		this.sourceId = sourceId;
	}

	@Transient
	public BaseEntity getSource() {
		return source;
	}

	public void setSource(BaseEntity source) {
		this.source = source;
	}

	@Column(name = "first_sort")
	public int getFirstSort() {
		return firstSort;
	}

	public void setFirstSort(int firstSort) {
		this.firstSort = firstSort;
	}

	@Column(name = "second_sort")
	public int getSecondSort() {
		return secondSort;
	}

	public void setSecondSort(int secondSort) {
		this.secondSort = secondSort;
	}

	@Column(name = "third_sort")
	public int getThirdSort() {
		return thirdSort;
	}

	public void setThirdSort(int thirdSort) {
		this.thirdSort = thirdSort;
	}

	@Transient
	public User getUser() {
		return user;
	}

	public void setUser(User user) {
		this.user = user;
	}

	@Transient
	public Page<Comment> getComments() {
		return comments;
	}

	public void setComments(Page<Comment> comments) {
		this.comments = comments;
	}

	@Column(name = "publish_time")
	public Date getPublishTime() {
		return publishTime;
	}

	public void setPublishTime(Date publishTime) {
		this.publishTime = publishTime;
	}

	@Transient
	public String getContentExt() {
		contentExt = StringUtil.formatContent(content);
		return contentExt;
	}

	public void setContentExt(String contentExt) {
		this.contentExt = contentExt;
	}

	@Transient
	public String getContentExt2() {
		contentExt2 = StringUtil.formatContentImgs(content);
		return contentExt2;
	}

	public void setContentExt2(String contentExt2) {
		this.contentExt2 = contentExt2;
	}

	@Transient
	public String getContentExt3() {
		contentExt3 = StringUtil.formatContentImgs2(content);
		return contentExt3;
	}

	public void setContentExt3(String contentExt3) {
		this.contentExt3 = contentExt3;
	}

	@Column(name = "from_url")
	public String getFromUrl() {
		return fromUrl;
	}

	public void setFromUrl(String fromUrl) {
		this.fromUrl = fromUrl;
	}

	public long getUuid() {
		return uuid;
	}

	public void setUuid(long uuid) {
		this.uuid = uuid;
	}

	public String getTags() {
		return tags;
	}

	public void setTags(String tags) {
		this.tags = tags;
	}

	@Override
	public String toString() {
		return ToStringBuilder.reflectionToString(this);
	}
}

Answer.java

package com.zuidaima.core.module;

/**
 **@author www.zuidaima.com
 2013-06-13 23:27:04
 */
import java.util.Date;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Table;
import javax.persistence.Transient;

import net.sf.json.JSONObject;

import org.apache.commons.lang.builder.ToStringBuilder;
import org.springframework.data.domain.Page;

import com.javaniu.core.constants.ModuleConstants;
import com.javaniu.core.util.StringUtil;

@Entity
@Table(name = "zuidaima_answer")
public class Answer extends BaseEntity {
	private long userId = 0;
	private User user;
	private String content;
	private String extendJson;
	private JSONObject extend;
	private long targetId = 0;
	private BaseEntity target;
	private int isPerfect = ModuleConstants.ANSWER_IS_PERFECT_NO;
	private int status = ModuleConstants.MODULE_STATUS_NORMAL;
	private Page<Comment> comments;
	private Date publishTime;
	private String contentExt;
	private String contentExt2;
	private int firstSort;
	private int secondSort;
	private int thirdSort;// comment count sort

	public Answer() {
		this.createTime = new Date();
		this.updateTime = createTime;
	}

	@Column(name = "user_id")
	public long getUserId() {
		return this.userId;
	}

	public void setUserId(long userId) {
		this.userId = userId;
	}

	public String getContent() {
		return this.content;
	}

	public void setContent(String content) {
		this.content = content;
	}

	@Column(name = "extend_json")
	public String getExtendJson() {
		return this.extendJson;
	}

	public void setExtendJson(String extendJson) {
		this.extendJson = extendJson;
	}

	@Transient
	public JSONObject getExtend() {
		if (extendJson == null) {
			extend = new JSONObject();
		} else {
			extend = JSONObject.fromObject(extendJson);
		}
		if (!extend
				.containsKey(ModuleConstants.ANSWER_EXTEND_JSON_DOWNLOAD_COUNT)) {
			extend.put(ModuleConstants.ANSWER_EXTEND_JSON_DOWNLOAD_COUNT, 0);
		}
		if (!extend.containsKey(ModuleConstants.ANSWER_EXTEND_JSON_FILE_SIZE)) {
			extend.put(ModuleConstants.ANSWER_EXTEND_JSON_FILE_SIZE, 0);
		}
		return extend;
	}

	public void setExtend(JSONObject extend) {
		this.extend = extend;
	}

	@Column(name = "target_id")
	public long getTargetId() {
		return this.targetId;
	}

	public void setTargetId(long targetId) {
		this.targetId = targetId;
	}

	@Transient
	public BaseEntity getTarget() {
		return target;
	}

	public void setTarget(BaseEntity target) {
		this.target = target;
	}

	@Column(name = "is_perfect")
	public int getIsPerfect() {
		return this.isPerfect;
	}

	public void setIsPerfect(int isPerfect) {
		this.isPerfect = isPerfect;
	}

	public int getStatus() {
		return this.status;
	}

	public void setStatus(int status) {
		this.status = status;
	}

	@Transient
	public User getUser() {
		return user;
	}

	public void setUser(User user) {
		this.user = user;
	}

	@Transient
	public Page<Comment> getComments() {
		return comments;
	}

	public void setComments(Page<Comment> comments) {
		this.comments = comments;
	}

	@Column(name = "publish_time")
	public Date getPublishTime() {
		return publishTime;
	}

	public void setPublishTime(Date publishTime) {
		this.publishTime = publishTime;
	}

	@Transient
	public String getContentExt() {
		contentExt = StringUtil.formatContent(content);
		return contentExt;
	}

	public void setContentExt(String contentExt) {
		this.contentExt = contentExt;
	}

	@Transient
	public String getContentExt2() {
		contentExt2 = StringUtil.formatContentImgs(content);
		return contentExt2;
	}

	public void setContentExt2(String contentExt2) {
		this.contentExt2 = contentExt2;
	}

	@Column(name = "first_sort")
	public int getFirstSort() {
		return firstSort;
	}

	public void setFirstSort(int firstSort) {
		this.firstSort = firstSort;
	}

	@Column(name = "second_sort")
	public int getSecondSort() {
		return secondSort;
	}

	public void setSecondSort(int secondSort) {
		this.secondSort = secondSort;
	}

	@Column(name = "third_sort")
	public int getThirdSort() {
		return thirdSort;
	}

	public void setThirdSort(int thirdSort) {
		this.thirdSort = thirdSort;
	}

	@Override
	public String toString() {
		return ToStringBuilder.reflectionToString(this);
	}
}