错误
请看一下GeoServer官方文档的警告
Warning:Currently the MySQL extension is unmaintained and carries unsupported status. While still usable, do not expect the same reliability as with other extensions.
没事不要特立独行使用MySQL当GeoServer的空间数据库，会变得不幸，而且不知道为什么会不幸。就比如我标题遇到的错误，一样的系统、数据库版本、一样的数据库名、一样的编码和排序、一样的表名，一样的字段，一样的数据，一份数据工作正常，一份数据会出现这个错误。
渲染界面报错：
后台错误详情：
ERROR [renderer.lite] - java.io.IOException: Error decoding wkb
java.lang.RuntimeException: java.io.IOException: Error decoding wkb
at org.geotools.jdbc.JDBCFeatureReader.readNextFeature(JDBCFeatureReader.java:389)
at org.geotools.jdbc.JDBCFeatureReader.hasNext(JDBCFeatureReader.java:332)
at org.geotools.data.store.ContentFeatureCollection$WrappingFeatureIterator.hasNext(ContentFeatureCollection.java:141)
at org.geoserver.feature.RetypingFeatureCollection$RetypingIterator.hasNext(RetypingFeatureCollection.java:112)
at org.geotools.data.crs.ForceCoordinateSystemIterator.hasNext(ForceCoordinateSystemIterator.java:121)
at org.geotools.renderer.lite.StreamingRenderer.drawPlain(StreamingRenderer.java:2664)
at org.geotools.renderer.lite.StreamingRenderer.processStylers(StreamingRenderer.java:2286)
at org.geotools.renderer.lite.StreamingRenderer.paint(StreamingRenderer.java:917)
at org.geoserver.wms.map.RenderedImageMapOutputFormat.produceMap(RenderedImageMapOutputFormat.java:540)
at org.geoserver.wms.map.RenderedImageMapOutputFormat.produceMap(RenderedImageMapOutputFormat.java:202)
at org.geoserver.wms.map.RenderedImageMapOutputFormat.produceMap(RenderedImageMapOutputFormat.java:82)
at org.geoserver.wms.GetMap.executeInternal(GetMap.java:344)
at org.geoserver.wms.GetMap.run(GetMap.java:203)
at org.geoserver.wms.GetMap.run(GetMap.java:113)
at org.geoserver.wms.DefaultWebMapService.getMap(DefaultWebMapService.java:250)
...
Caused by: java.io.IOException: Error decoding wkb
at org.geotools.data.mysql.MySQLDialectBasic.decodeGeometryValue(MySQLDialectBasic.java:222)
at org.geotools.jdbc.SQLDialect.decodeGeometryValue(SQLDialect.java:764)
at org.geotools.jdbc.JDBCFeatureReader.readNextFeature(JDBCFeatureReader.java:381)
... 153 more
Caused by: org.locationtech.jts.io.ParseException: Attempt to read past end of input
at org.locationtech.jts.io.ByteOrderDataInStream.read(ByteOrderDataInStream.java:142)
at org.locationtech.jts.io.ByteOrderDataInStream.readInt(ByteOrderDataInStream.java:107)
at org.locationtech.jts.io.WKBReader.readGeometry(WKBReader.java:229)
at org.locationtech.jts.io.WKBReader.read(WKBReader.java:191)
at org.locationtech.jts.io.WKBReader.read(WKBReader.java:159)
at org.geotools.data.mysql.MySQLDialectBasic.decodeGeometryValue(MySQLDialectBasic.java:219)
... 155 more
GeoServer使用MySQL
GeoServer默认是不支持MySQL的，需要安装相应的扩展组件才支持。比起根据官方文档中 Installing the MySQL extension的指引下载MySQL扩展组件，我更推荐到GeoTools官网下载对应版本的包，然后把其中的gt-jdbc-mysql-x.x.jar和mysql-connector-java-x.x.x.jar复制到geoserver/webapps/geoserver/WEB-INF/lib文件夹下，如果重启GeoServer之后可以添加MySQL数据源，发布图层、正常预览，那么恭喜，不需要往下看了，如果遇到我一样的错误，就很不幸，需要了解一点点Java开发才能解决问题。
解决方法
GeoTools是一个开源的Java 空间数据操作库，GeoServer里大量使用了GeoTools的库，虽然也没法调试吧，但是通过改代码替换包的形式，一点点追溯下来，最后发现不知道什么原因，他在读MySQL的时候会重复读取主键，比如主键是ID，那他读出来的字段列表会是ID,ID,filed1,the_geom。理论上the_geom的index是3（从1开始算），但有两列ID之后，用index=3读出来的会是field1字段，就导致读出来的并不是空间数据，强行解析成空间数据的时候就会出错，所以就会报错Error decoding wkb。
知道了原因，解决起来就简单了，在gt-jdbc这个包里HeuristicPrimaryKeyFinder.java文件的createPrimaryKey方法，加入如下代码，在构造主键时遇到重复的就跳过就可以了：
Boolean exist = false;
for (int i = 0; i < cols.size(); i++) {
if (cols.get(i).name.equals(columnName)) {
exist = true;
break;
}
}
if (exist) {
continue;
}
加了之后的createPrimaryKey方法完整代码：
/*
* Creates a key from a primary key or unique index.
*/
PrimaryKey createPrimaryKey(
JDBCDataStore store,
ResultSet index,
DatabaseMetaData metaData,
String databaseSchema,
String tableName,
Connection cx)
throws SQLException {
ArrayList<PrimaryKeyColumn> cols = new ArrayList<>();
while (index.next()) {
String columnName = index.getString("COLUMN_NAME");
// work around. For some reason the first record returned is always 'empty'
// this was tested on Oracle and Postgres databases
if (columnName == null) {
continue;
}
// Alter By ZXHM
Boolean exist = false;
for (int i = 0; i < cols.size(); i++) {
if (cols.get(i).name.equals(columnName)) {
exist = true;
break;
}
}
if (exist) {
continue;
}
// look up the type ( should only be one row )
ResultSet columns =
metaData.getColumns(
null,
store.escapeNamePattern(metaData, databaseSchema),
store.escapeNamePattern(metaData, tableName),
store.escapeNamePattern(metaData, columnName));
Class columnType;
try {
columns.next();
columnType = store.getSQLDialect().getMapping(columns, cx);
if (columnType == null) {
int binding = columns.getInt("DATA_TYPE");
columnType = store.getMapping(binding);
if (columnType == null) {
LOGGER.warning("No class for sql type " + binding);
columnType = Object.class;
}
}
} finally {
store.closeSafe(columns);
}
// determine which type of primary key we have
PrimaryKeyColumn col = null;
// 1. Auto Incrementing?
Statement st = cx.createStatement();
try {
// not actually going to get data
st.setFetchSize(1);
StringBuffer sql = new StringBuffer();
sql.append("SELECT ");
store.getSQLDialect().encodeColumnName(null, columnName, sql);
sql.append(" FROM ");
store.encodeTableName(tableName, sql, null);
sql.append(" WHERE 0=1");
LOGGER.log(Level.FINE, "Grabbing table pk metadata: {0}", sql);
ResultSet rs = st.executeQuery(sql.toString());
try {
if (rs.getMetaData().isAutoIncrement(1)) {
col = new AutoGeneratedPrimaryKeyColumn(columnName, columnType);
}
} finally {
store.closeSafe(rs);
}
} finally {
store.closeSafe(st);
}
// 2. Has a sequence?
if (col == null) {
try {
String sequenceName =
store.getSQLDialect()
.getSequenceForColumn(
databaseSchema, tableName, columnName, cx);
if (sequenceName != null) {
col = new SequencedPrimaryKeyColumn(columnName, columnType, sequenceName);
}
} catch (Exception e) {
// log the exception , and continue on
LOGGER.log(
Level.WARNING,
"Error occured determining sequence for "
+ columnName
+ ", "
+ tableName,
e);
}
}
if (col == null) {
col = new NonIncrementingPrimaryKeyColumn(columnName, columnType);
}
cols.add(col);
}
if (!cols.isEmpty()) {
return new PrimaryKey(tableName, cols);
}
return null;
}
我只是稍微了解一点Java，不知道我这个避免重复主键的写法有没有啥问题，现在就是能用就行。最后自己打包替换掉原有的gt-jdbc-x.x.jar然后重启GeoServer就可以了。当然这仅仅只是我遇到的情况，不保证使用MySQL数据库发生Error decoding wkb的报错都是这个情况。总而言之，不到万不得已，不要用MySQL作为GeoServer的空间数据库。
