在上一篇文章里面分析到，Spring JDBC有三个异常转换器，其中，SQLErrorCodeSQLExceptionTranslator.doTranslate()方法有多处接口可共开发人员进行扩展，下面一一介绍。
方法一，继承SQLErrorCodeSQLExceptionTranslator，重写customTranslate()方法，既从如下扩展：
// First, try custom translation from overridden method.DataAccessException dex = customTranslate(task, sql, sqlEx);if (dex != null) {return dex;}先自定义一个异常类，必须继承自DataAccessException,DataAccessException 有两个构造器，如果希望打印原异常信息，就覆盖带有Throwable参数的，如果覆盖只有msg参数的构造器，原异常信息不会被打印。
/*** Constructor for DataAccessException.* @param msg the detail message*/public DataAccessException(String msg) {super(msg);}/*** Constructor for DataAccessException.* @param msg the detail message* @param cause the root cause (usually from using a underlying* data access API such as JDBC)*/public DataAccessException(@Nullable String msg, @Nullable Throwable cause) {super(msg, cause);}这里，覆盖第二个带Throwable参数的：
public class CustomSQLException extends DataAccessException {public CustomSQLException(String msg, Throwable cause) {super(msg, cause); }}
然后定义一个异常转换器，必须继承自SQLErrorCodeSQLExceptionTranslator，重写customTranslate()方法，
public class CustomSQLErrorCodeTranslator extends SQLErrorCodeSQLExceptionTranslator {@Override protected DataAccessException customTranslate(String task, String sql,SQLException sqlEx) { return new CustomSQLException("扩展方法一") ;} }用自定义转换器替换默认的SQLErrorCodeSQLExceptionTranslator转换器
jdbcTemplate.setExceptionTranslator(new CustomSQLErrorCodeTranslator());刻意制造异常SQL，执行：
Exception in thread "AWT-EventQueue-0" com.aia.pos.horse.db.execute.CustomSQLException: 扩展方法一; nested exception is java.sql.BatchUpdateException: String or binary data would be truncated.at com.aia.pos.horse.db.execute.CustomSQLErrorCodeTranslator.customTranslate(CustomSQLErrorCodeTranslator.java:13)at org.springframework.jdbc.support.SQLErrorCodeSQLExceptionTranslator.doTranslate(SQLErrorCodeSQLExceptionTranslator.java:183)at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:72)at org.springframework.jdbc.core.JdbcTemplate.translateException(JdbcTemplate.java:1400)at org.springframework.jdbc.core.JdbcTemplate.execute(JdbcTemplate.java:388)at org.springframework.jdbc.core.JdbcTemplate.batchUpdate(JdbcTemplate.java:576)成功触发。
方法二，自定义的异常处理转换器实现自SQLExceptionTranslator，既从如下扩展：
// Next, try the custom SQLException translator, if available.if (this.sqlErrorCodes != null) {SQLExceptionTranslator customTranslator = this.sqlErrorCodes.getCustomSqlExceptionTranslator();if (customTranslator != null) {DataAccessException customDex = customTranslator.translate(task, sql, sqlEx);if (customDex != null) {return customDex;}}}修改CustomSQLErrorCodeTranslator实现SQLExceptionTranslator：
public class CustomSQLErrorCodeTranslator implements SQLExceptionTranslator {public DataAccessException translate(String task, String sql, SQLException ex) { return new CustomSQLException("扩展方法二",ex);}}将自定义转换器传给SQLErrorCodes的customSqlExceptionTranslator，
if(jdbcTemplate.getExceptionTranslator() instanceof SQLErrorCodeSQLExceptionTranslator ){SQLErrorCodeSQLExceptionTranslator translator=(SQLErrorCodeSQLExceptionTranslator) jdbcTemplate.getExceptionTranslator();translator.getSqlErrorCodes().setCustomSqlExceptionTranslatorClass(CustomSQLErrorCodeTranslator.class);}执行：
Exception in thread "AWT-EventQueue-0" com.aia.pos.horse.db.execute.CustomSQLException: 扩展方法二; nested exception is java.sql.BatchUpdateException: String or binary data would be truncated.at com.aia.pos.horse.db.execute.CustomSQLErrorCodeTranslator.translate(CustomSQLErrorCodeTranslator.java:12)at org.springframework.jdbc.support.SQLErrorCodeSQLExceptionTranslator.doTranslate(SQLErrorCodeSQLExceptionTranslator.java:192)at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:72)at org.springframework.jdbc.core.JdbcTemplate.translateException(JdbcTemplate.java:1400)成功触发。
方法三，利用SQLErrorCodes的customTranslations属性进行扩展，既从如下扩展：
CustomSQLErrorCodesTranslation[] customTranslations = this.sqlErrorCodes.getCustomTranslations();if (customTranslations != null) {for (CustomSQLErrorCodesTranslation customTranslation : customTranslations) {if (Arrays.binarySearch(customTranslation.getErrorCodes(), errorCode) >= 0) {if (customTranslation.getExceptionClass() != null) {DataAccessException customException = createCustomException(task, sql, sqlEx, customTranslation.getExceptionClass());if (customException != null) {logTranslation(task, sql, sqlEx, true);return customException;}}}}}这种方式也比较简单，只需要实例化customTranslations就可以了。CustomSQLErrorCodesTranslation有两个属性，errorCodes和exceptionClass,既一个异常类对应一对应一组error code ,异常类我们还用CustomSQLException，codes随便写一些 。
/*** JavaBean for holding custom JDBC error codes translation for a particular* database. The "exceptionClass" property defines which exception will be* thrown for the list of error codes specified in the errorCodes property.** @author Thomas Risberg* @since 1.1* @see SQLErrorCodeSQLExceptionTranslator*/
public class CustomSQLErrorCodesTranslation {private String[] errorCodes = new String[0];@Nullableprivate Class<?> exceptionClass;假设程序抛出以下异常 ，
Exception in thread "AWT-EventQueue-0" org.springframework.dao.DataIntegrityViolationException: StatementCallback; SQL [insert into nposrref (ORGID,CURCODE,REFTYPE,CODE,VALUE,DESCRIPTION,SEQ,filter1,filter2,filter3,filter4,filter5) values ('N00001','RMB','MSGN00001N00001N001N0001','M71030','保单有其它科目款项或借款，请先人工处理。',NULL,NULL,NULL,NULL,NULL,NULL,'SPRINT6')String or binary data would be truncated.; nested exception is java.sql.BatchUpdateException: String or binary data would be truncated.at org.springframework.jdbc.support.SQLStateSQLExceptionTranslator.doTranslate(SQLStateSQLExceptionTranslator.java:104)at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:72)at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:81)at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:81)调试得知，该异常对应的 sql error code =8152,于是，
if( jdbcTemplate.getExceptionTranslator() instanceof SQLErrorCodeSQLExceptionTranslator ){SQLErrorCodeSQLExceptionTranslator translator=(SQLErrorCodeSQLExceptionTranslator) jdbcTemplate.getExceptionTranslator();CustomSQLErrorCodesTranslation tran=new CustomSQLErrorCodesTranslation();tran.setErrorCodes("8152");tran.setExceptionClass(CustomSQLException.class); translator.getSqlErrorCodes().setCustomTranslations(tran); }执行，
Exception in thread "AWT-EventQueue-0" com.aia.pos.horse.db.execute.CustomSQLException: 扩展方法三; nested exception is java.sql.BatchUpdateException: String or binary data would be truncated.at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)at java.lang.reflect.Constructor.newInstance(Constructor.java:422)at org.springframework.jdbc.support.SQLErrorCodeSQLExceptionTranslator.createCustomException(SQLErrorCodeSQLExceptionTranslator.java:378)at org.springframework.jdbc.support.SQLErrorCodeSQLExceptionTranslator.doTranslate(SQLErrorCodeSQLExceptionTranslator.java:222)at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:72)at org.springframework.jdbc.core.JdbcTemplate.translateException(JdbcTemplate.java:1400)成功触发。
方法四，通过扩展 sql-error-codes.xml 进行扩展。
sql-error-codes.xml既是error code 配置文件,又是spring bean 的配置文件，所以我们可以在配置文件中通过set方法注入error codes 和 exceptionClass 值，举个栗子 ，假设现在有个新的数据库叫customDB:
<bean id="customDB" class="org.springframework.jdbc.support.SQLErrorCodes"><property name="databaseProductName"><value>customDB</value></property><property name="customTranslations"><list><bean class="org.springframework.jdbc.support.CustomSQLErrorCodesTranslation"><property name="errorCodes">10000</property><property name="exceptionClass">test.CustomSQLException</property></bean></list></property></bean>
方法四也是利用sqlErrorCodes 的customTranslations，属性进行修改，只不过方法三通过代码扩展，而方法四通过配置文件修改。
当然开发者也可以在 sql--error-codes.xml修改增加或删除一些配置。只需要参照已存在的数据库进行配置就可以了，到此，扩展转换器就分析完了。