解决mybatis在oracle中null的问题
使用mybatis时遇到Error setting null parameter异常，常用的解决方式是在sql中指定jdbcType，这样的写法感觉有点罗嗦，后来参考spring jdbc中的实现方式，改写了mybatis中的BaseTypeHandler类，经测试ok。
以下是修改的类文件，修改的地方为19 ~ 36行。
?
package org.apache.ibatis.type;
import java.sql.CallableStatement;
import java.sql.DatabaseMetaData;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Types;
public abstract class BaseTypeHandler implements TypeHandler {
?public void setParameter(PreparedStatement ps, int i, Object parameter, JdbcType jdbcType) throws SQLException {
??if (parameter == null) {
???if (jdbcType == null) {
????try {
?????boolean useSetObject = false;
?????int sqlType = Types.NULL;
?????try {
??????DatabaseMetaData dbmd = ps.getConnection().getMetaData();
??????String databaseProductName = dbmd.getDatabaseProductName();
??????String jdbcDriverName = dbmd.getDriverName();
??????if (databaseProductName.startsWith("Informix")
????????|| jdbcDriverName.startsWith("Microsoft SQL Server")) {
???????useSetObject = true;
??????} else if (databaseProductName.startsWith("Oracle") || databaseProductName.startsWith("DB2") || jdbcDriverName.startsWith("jConnect")
????????|| jdbcDriverName.startsWith("SQLServer") || jdbcDriverName.startsWith("Apache Derby")) {
???????sqlType = Types.VARCHAR;
??????}
?????} catch (Throwable ex) {
??????throw new TypeException("Could not check database or driver name", ex);
?????}
?????if (useSetObject) {
??????ps.setObject(i, null);
?????} else {
??????ps.setNull(i, sqlType);
?????}
????} catch (SQLException e) {
?????throw new TypeException(
???????"Error setting null parameter.? Most JDBC drivers require that the JdbcType must be specified for all nullable parameters. Cause: "
?????????+ e, e);
????}
???} else {
????ps.setNull(i, jdbcType.TYPE_CODE);
???}
??} else {
???setNonNullParameter(ps, i, parameter, jdbcType);
??}
?}
?public Object getResult(ResultSet rs, String columnName) throws SQLException {
??Object result = getNullableResult(rs, columnName);
??if (rs.wasNull()) {
???return null;
??} else {
???return result;
??}
?}
?public Object getResult(CallableStatement cs, int columnIndex) throws SQLException {
??Object result = getNullableResult(cs, columnIndex);
??if (cs.wasNull()) {
???return null;
??} else {
???return result;
??}
?}
?public abstract void setNonNullParameter(PreparedStatement ps, int i, Object parameter, JdbcType jdbcType)
???throws SQLException;
?public abstract Object getNullableResult(ResultSet rs, String columnName) throws SQLException;
?public abstract Object getNullableResult(CallableStatement cs, int columnIndex) throws SQLException;
}
