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SamplePojo.java
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"; } }
ResultSetMapper.java
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 = rs.getObject(_iterator + 1); // iterating over outputClass attributes to check if any attribute has 'Column' annotation with matching 'name' value 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 { return null; } } catch (IllegalAccessException e) { e.printStackTrace(); } catch (SQLException e) { e.printStackTrace(); } catch (InstantiationException e) { e.printStackTrace(); } catch (InvocationTargetException e) { e.printStackTrace(); } return outputList; } }
使用方法
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(); // simple JDBC code to run SQL query and populate resultSet - END List<SamplePojo> pojoList = resultSetMapper.mapRersultSetToObject(resultSet, SamplePojo.class); // print out the list retrieved from database 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(); } } }