mybatis中分页插件的使用
1、@Intercepts({@Signature(type=StatementHandler.class,method="prepare",args={Connection.class})})
public class PagePlugin implements Interceptor {
private static String dialect = ""; //数据库方言
private static String pageSqlId = ""; //mapper.xml中需要拦截的ID(正则匹配)
public Object intercept(Invocation ivk) throws Throwable {
// TODO Auto-generated method stub
if(ivk.getTarget() instanceof RoutingStatementHandler){
RoutingStatementHandler statementHandler = (RoutingStatementHandler)ivk.getTarget();
BaseStatementHandler delegate = (BaseStatementHandler) ReflectHelper.getValueByFieldName(statementHandler, "delegate");
MappedStatement mappedStatement = (MappedStatement) ReflectHelper.getValueByFieldName(delegate, "mappedStatement");
2、if(mappedStatement.getId().matches(pageSqlId)){ //拦截需要分页的SQL
BoundSql boundSql = delegate.getBoundSql();
Object parameterObject = boundSql.getParameterObject();//分页SQL<select>中parameterType属性对应的实体参数，即Mapper接口中执行分页方法的参数,该参数不得为空
if(parameterObject==null){
throw new NullPointerException("parameterObject尚未实例化！");
}
3、else{
Connection connection = (Connection) ivk.getArgs()[0];
String sql = boundSql.getSql();
//String countSql = "select count(0) from (" + sql+ ") as tmp_count"; //记录统计
String fhsql = sql;
String countSql = "select count(0) from (" + fhsql+ ") tmp_count"; //记录统计 == oracle 加 as 报错(SQL command not properly ended)
PreparedStatement countStmt = connection.prepareStatement(countSql);
1、BoundSql countBS = new BoundSql(mappedStatement.getConfiguration(),countSql,boundSql.getParameterMappings(),parameterObject);
setParameters(countStmt,mappedStatement,countBS,parameterObject);
ResultSet rs = countStmt.executeQuery();
int count = 0;
if (rs.next()) {
count = rs.getInt(1);
}
2、rs.close();
countStmt.close();
//System.out.println(count);
Page page = null;
if(parameterObject instanceof Page){ //参数就是Page实体
page = (Page) parameterObject;
page.setEntityOrField(true);
page.setTotalResult(count);
}else{ //参数为某个实体，该实体拥有Page属性
Field pageField = ReflectHelper.getFieldByFieldName(parameterObject,"page");
3、if(pageField!=null){
page = (Page) ReflectHelper.getValueByFieldName(parameterObject,"page");
if(page==null)
page = new Page();
page.setEntityOrField(false);
page.setTotalResult(count);
ReflectHelper.setValueByFieldName(parameterObject,"page", page); //通过反射，对实体对象设置分页对象
}else{
throw new NoSuchFieldException(parameterObject.getClass().getName()+"不存在 page 属性！");
}
}
String pageSql = generatePageSql(sql,page);
ReflectHelper.setValueByFieldName(boundSql, "sql", pageSql); //将分页sql语句反射回BoundSql.
}
}
}
return ivk.proceed();
}
/**
* 对SQL参数(?)设值,参考org.apache.ibatis.executor.parameter.DefaultParameterHandler
* @param ps
* @param mappedStatement
* @param boundSql
* @param parameterObject
* @throws SQLException
*/
private void setParameters(PreparedStatement ps,MappedStatement mappedStatement,BoundSql boundSql,Object parameterObject) throws SQLException {
ErrorContext.instance().activity("setting parameters").object(mappedStatement.getParameterMap().getId());
List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();
if (parameterMappings != null) {
Configuration configuration = mappedStatement.getConfiguration();
TypeHandlerRegistry typeHandlerRegistry = configuration.getTypeHandlerRegistry();
MetaObject metaObject = parameterObject == null ? null: configuration.newMetaObject(parameterObject);
for (int i = 0; i < parameterMappings.size(); i++) {
ParameterMapping parameterMapping = parameterMappings.get(i);
if (parameterMapping.getMode() != ParameterMode.OUT) {
Object value;
String propertyName = parameterMapping.getProperty();
PropertyTokenizer prop = new PropertyTokenizer(propertyName);
if (parameterObject == null) {
value = null;
} else if (typeHandlerRegistry.hasTypeHandler(parameterObject.getClass())) {
value = parameterObject;
} else if (boundSql.hasAdditionalParameter(propertyName)) {
value = boundSql.getAdditionalParameter(propertyName);
} else if (propertyName.startsWith(ForEachSqlNode.ITEM_PREFIX)&& boundSql.hasAdditionalParameter(prop.getName())) {
value = boundSql.getAdditionalParameter(prop.getName());
if (value != null) {
value = configuration.newMetaObject(value).getValue(propertyName.substring(prop.getName().length()));
}
} else {
value = metaObject == null ? null : metaObject.getValue(propertyName);
}
TypeHandler typeHandler = parameterMapping.getTypeHandler();
if (typeHandler == null) {
throw new ExecutorException("There was no TypeHandler found for parameter "+ propertyName + " of statement "+ mappedStatement.getId());
}
typeHandler.setParameter(ps, i + 1, value, parameterMapping.getJdbcType());
}
}
}
}
/**
* 根据数据库方言，生成特定的分页sql
* @param sql
* @param page
* @return
*/
private String generatePageSql(String sql,Page page){
if(page!=null && Tools.notEmpty(dialect)){
StringBuffer pageSql = new StringBuffer();
if("mysql".equals(dialect)){
pageSql.append(sql);
pageSql.append(" limit "+page.getCurrentResult()+","+page.getShowCount());
}
return pageSql.toString();
}else{
return sql;
}
}
public Object plugin(Object arg0) {
// TODO Auto-generated method stub
return Plugin.wrap(arg0, this);
}
4、public void setProperties(Properties p) {
dialect = p.getProperty("dialect");
if (Tools.isEmpty(dialect)) {
try {
throw new PropertyException("dialect property is not found!");
} catch (PropertyException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
pageSqlId = p.getProperty("pageSqlId");
if (Tools.isEmpty(pageSqlId)) {
try {
throw new PropertyException("pageSqlId property is not found!");
} catch (PropertyException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}