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如何把ResultSet转换成Java对象
有时候我们不想使用任何框架,但又需要用JDBC实现类似于iBATIS的orm映射功能,把一个ResultSet转换成我们的JavaBeans,我们可以模仿iBATIS的方式自己写一个ResultSetMapper实现类,利用反射原理把ResultSet转换成一个JavaBeans,下面是网上的一个开源实现,主要用到的是注解和反射机制,我们先看一下使用效果:
package com.heaven.mapper; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.util.List; public class SampleMain { public static void main(String ...args){ try { ResultSetMapper<SamplePojo> resultSetMapper = new ResultSetMapper<SamplePojo>(); ResultSet resultSet = null; // simple JDBC code to run SQL query and populate resultSet - START Class.forName("sun.jdbc.odbc.JdbcOdbcDriver"); String database = "jdbc:odbc:AkDb"; Connection connection = DriverManager.getConnection( database ,"",""); PreparedStatement statement = connection.prepareStatement("SELECT * FROM UsersSample"); resultSet = statement.executeQuery(); /******************************/ List<SamplePojo> pojoList = resultSetMapper.mapRersultSetToObject(resultSet, SamplePojo.class); /******************************/ if(pojoList != null){ for(SamplePojo pojo : pojoList){ System.out.println(pojo); } }else{ System.out.println("ResultSet is empty. Please check if database table is empty"); } connection.close(); } catch (ClassNotFoundException e) { e.printStackTrace(); } catch (SQLException e) { e.printStackTrace(); } } }如上图所示,把ResultSet转换成我们的JavaPojo对象只需要调用ResultSetMapper的一个方法即可完成,使用起来非常方便。
下面是ResultSetMapper源代码:
package com.heaven.mapper; 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; public class ResultSetMapper<T> { @SuppressWarnings("unchecked") public List<T> mapRersultSetToObject(ResultSet rs, Class outputClass) { List<T> outputList = null; try { // make sure resultset is not null if (rs != null) { // 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 = http://www.mamicode.com/rs.getObject(_iterator + 1);> 使用注解的pojo对象:
<pre name="code" class="java">package com.heaven.mapper; import javax.persistence.Column; import javax.persistence.Entity; @Entity public class SamplePojo { @Column(name="User_Id") private int id; @Column(name="User_Name") private String name; @Column(name="Address") private String address; @Column(name="Gender") private boolean gender; public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getAddress() { return address; } public void setAddress(String address) { this.address = address; } public boolean isGender() { return gender; } public void setGender(boolean gender) { this.gender = gender; } @Override public String toString() { return "id: " + id + "\n" + "name: " + name + "\n"+ "address: " + address + "\n" + "gender: " + (gender ? "Male" : "Female") + "\n\n"; } }
如何把ResultSet转换成Java对象
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