import java.util.Properties;
import org.apache.ibatis.executor.Executor;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.mapping.MappedStatement.Builder;
import org.apache.ibatis.mapping.SqlSource;
import org.apache.ibatis.plugin.Interceptor;
import org.apache.ibatis.plugin.Intercepts;
import org.apache.ibatis.plugin.Invocation;
import org.apache.ibatis.plugin.Plugin;
import org.apache.ibatis.plugin.Signature;
import org.apache.ibatis.session.ResultHandler;
import org.apache.ibatis.session.RowBounds;
import com.gm.common.orm.mybatis.dialect.Dialect;
import com.gm.common.utils.PropertiesHelper;
/**
* 为Mybatis提供基于方言(Dialect)的分页查询的插件
*
* 将拦截Executor.query()方法实现分页方言的插入.
*
* 配置文件内容:
*
* <pre>
* <plugins>
* <plugin interceptor="com.gm.common.orm.mybatis.plugin.OffsetLimitInterceptor">
* <property name="dialectClass" value="com.gm.common.orm.mybatis.dialect.MySQLDialect"/>
* </plugin>
* </plugins>
* </pre>
*/
@Intercepts({@Signature(type=Executor.class,method="query",args={MappedStatement.class,Object.class,RowBounds.class,ResultHandler.class})})
public class OffsetLimitInterceptor implements Interceptor {
static int MAPPED_STATEMENT_INDEX = 0;
static int PARAMETER_INDEX = 1;
static int ROWBOUNDS_INDEX = 2;
static int RESULT_HANDLER_INDEX = 3;
Dialect dialect;
public Object intercept(Invocation invocation) throws Throwable {
processIntercept(invocation.getArgs());
return invocation.proceed();
}
void processIntercept(final Object[] queryArgs) {
// queryArgs = query(MappedStatement ms, Object parameter, RowBounds
// rowBounds, ResultHandler resultHandler)
MappedStatement ms = (MappedStatement) queryArgs[MAPPED_STATEMENT_INDEX];
Object parameter = queryArgs[PARAMETER_INDEX];
final RowBounds rowBounds = (RowBounds) queryArgs[ROWBOUNDS_INDEX];
int offset = rowBounds.getOffset();
int limit = rowBounds.getLimit();
if (dialect.supportsLimit()
&& (offset != RowBounds.NO_ROW_OFFSET || limit != RowBounds.NO_ROW_LIMIT)) {
BoundSql boundSql = ms.getBoundSql(parameter);
String sql = boundSql.getSql().trim();
if (dialect.supportsLimitOffset()) {
sql = dialect.getLimitString(sql, offset, limit);
offset = RowBounds.NO_ROW_OFFSET;
} else {
sql = dialect.getLimitString(sql, 0, limit);
}
limit = RowBounds.NO_ROW_LIMIT;
queryArgs[ROWBOUNDS_INDEX] = new RowBounds(offset, limit);
BoundSql newBoundSql = new BoundSql(ms.getConfiguration(),
sql, boundSql.getParameterMappings(), boundSql
.getParameterObject());
MappedStatement newMs = copyFromMappedStatement(ms,
new BoundSqlSqlSource(newBoundSql));
queryArgs[MAPPED_STATEMENT_INDEX] = newMs;
}
}
// see: MapperBuilderAssistant
private MappedStatement copyFromMappedStatement(MappedStatement ms,
SqlSource newSqlSource) {
Builder builder = new MappedStatement.Builder(ms
.getConfiguration(), ms.getId(), newSqlSource, ms
.getSqlCommandType());
builder.resource(ms.getResource());
builder.fetchSize(ms.getFetchSize());
builder.statementType(ms.getStatementType());
builder.keyGenerator(ms.getKeyGenerator());
builder.keyProperty(ms.getKeyProperty());
// setStatementTimeout()
builder.timeout(ms.getTimeout());
// setStatementResultMap()
builder.parameterMap(ms.getParameterMap());
// setStatementResultMap()
builder.resultMaps(ms.getResultMaps());
builder.resultSetType(ms.getResultSetType());
// setStatementCache()
builder.cache(ms.getCache());
builder.flushCacheRequired(ms.isFlushCacheRequired());
builder.useCache(ms.isUseCache());
return builder.build();
}
public Object plugin(Object target) {
return Plugin.wrap(target, this );
}
public void setProperties(Properties properties) {
String dialectClass = new PropertiesHelper(properties)
.getRequiredString("dialectClass");
try {
dialect = (Dialect) Class.forName(dialectClass)
.newInstance();
} catch (Exception e) {
throw new RuntimeException(
"cannot create dialect instance by dialectClass:"
+ dialectClass, e);
}
System.out.println(OffsetLimitInterceptor.class.getSimpleName()
+ ".dialect=" + dialectClass);
}
public static class BoundSqlSqlSource implements SqlSource {
BoundSql boundSql;
public BoundSqlSqlSource(BoundSql boundSql) {
this .boundSql = boundSql;
}
public BoundSql getBoundSql(Object parameterObject) {
return boundSql;
}
}
}
我的参考: https ://www.java2s.com/Open-Source/Java-Document-2/UnTagged/gmc/com/gm/common/orm/mybatis/plugin/OffsetLimitInterceptor.java.htm