ResultSet转成java类对象

在做web开发时遇到一个事情：

需要从mysql数据表中查询数据并遍历查询结果

这样最简单的方式是：查询到结果根据表中字段列表的顺序来一个个获取字段，但这样需要记住字段的顺序，操作起来不是那么方便。因此便想可不可以把查询结果

ResultSet转化成java的实例对象，然后利用类对象的get方法，这样会方便清晰很多。

查了下，有很多可以参考，于是参考着有了自己的代码，如下：

1.mapper函数：

package com.alibaba.search.offline.oddiff.service;

import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import javax.persistence.Column;
import javax.persistence.Entity;
import org.apache.commons.beanutils.BeanUtils;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import com.jcraft.jsch.Logger;

//import com.alibaba.druid.sql.ast.statement.SQLCreateViewStatement.Column;

public class OddiffResultSetMapper<T> {
protected static Log logger = LogFactory.getLog(OddiffResultSetMapper.class);
@SuppressWarnings("unchecked")
public List<T> mapRersultSetToObject(ResultSet rs, Class outputClass) {
List<T> outputList = null;
try {
// make sure resultset is not null
if (rs != null) {
logger.info("rs:"+rs);
// check if outputClass has 'Entity' annotation
if (outputClass.isAnnotationPresent(Entity.class)) {
// get the resultset metadata
ResultSetMetaData rsmd = rs.getMetaData();
// get all the attributes of outputClass
Field[] fields = outputClass.getDeclaredFields();
while (rs.next()) {
T bean = (T) outputClass.newInstance();
for (int _iterator = 0; _iterator < rsmd.getColumnCount(); _iterator++) {
// getting the SQL column name
String columnName = rsmd.getColumnName(_iterator + 1);

// reading the value of the SQL column
Object columnValue = rs.getObject(_iterator + 1);
logger.info("columnName:"+columnName+",value:"+columnValue);
for (Field field : fields) {
if (field.isAnnotationPresent(Column.class)) {
Column column = field.getAnnotation(Column.class);
if (column.name().equalsIgnoreCase(columnName) && columnValue != null) {
BeanUtils.setProperty(bean, field.getName(), columnValue);
break;
}
}
}
}
if (outputList == null) {
outputList = new ArrayList<T>();
}
outputList.add(bean);
}

} else {
// throw some error
}
} else {
logger.info("rs is null");
return null;
}
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
} catch (InstantiationException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
return outputList;
}
}

2.类对象的声明：

package com.alibaba.search.offline.oddiff.service;

import java.util.Date;

import javax.persistence.Column;

import javax.persistence.Entity;

@Entity

public class OddiffEntity {

@Column(name="id")

private Integer Id;

@Column(name="user_name")

private String userName;

@Column(name="app_name")

private String appName;

@Column(name="online_version")

private String onlineVersion;

@Column(name="oa_version")

private String oaVersion;

@Column(name="data_name")

private String dataName;

@Column(name="start_time")

private String startTime;

@Column(name="end_time")

private String endTime;

@Column(name="commit_time")

private String commitTime;

@Column(name="duration_time")

private String durationTime;

@Column(name="status")

private String status;

@Column(name="log_file")

private String logFile;

public void setId(Integer id) {

this.Id = id;

}

public Integer getId() {

return Id;

}

public void setUserName(String userName) {

this.userName = userName;

}

public String getUserName() {

return userName;

}

public void setAppName(String appName) {

this.appName = appName;

}

public String getAppName() {

return appName;

}

public void setOnlineVersion(String onlineVersion) {

this.onlineVersion = onlineVersion;

}

public String getOnlineVersion() {

return onlineVersion;

}

public void setOaVersion(String oaVersion) {

this.oaVersion = oaVersion;

}

public String getOaVersion() {

return this.oaVersion;

}

public void setDataName(String dataName) {

this.dataName = dataName;

}

public String getDataName() {

return dataName;

}

public void setStartTime(String startTime) {

this.startTime = startTime;

}

public String getStartTime() {

return startTime;

}

public void setEndTime(String endTime) {

this.endTime = endTime;

}

public String getEndTime() {

return endTime;

}

public void setCommitTime(String commitTime) {

this.commitTime = commitTime;

}

public String getCommitTime() {

return commitTime;

}

public void setDurationTime(String durationTime) {

this.durationTime = durationTime;

}

public String getDurationTime() {

return durationTime;

}

public void setStatus(String status) {

this.status = status;

}

public String getStatus() {

return status;

}

public void setLogFile(String logFile) {

this.logFile = logFile;

}

public String getLogFile() {

return logFile;

}

@Override

public String toString() {

return  "id: " + Id + "\n" +

"user_name: " + userName + "\n"+

"app_name: " + appName + "\n" ;

}

}

3.真的转化：

public static List<OddiffEntity> Execute_select(Connection conn, String sql) {

if (conn==null)

conn = getConn();//此处为通过自己写的方法getConn()获得连接

OddiffResultSetMapper<OddiffEntity> resultSetMapper = new OddiffResultSetMapper<OddiffEntity>();

try {

Statement stmt = conn.createStatement();

ResultSet rs = stmt.executeQuery(sql);

logger.info("---sql:"+sql);

logger.info("select result:"+rs.getFetchSize());

List<OddiffEntity> pojoList = resultSetMapper.mapRersultSetToObject(rs, OddiffEntity.class);

if (pojoList!=null){

for (OddiffEntity job:pojoList){

logger.info("job:"+job.toString());

}

}

return pojoList;

} catch (SQLException e) {

e.printStackTrace();

}

return null;

}